diff --git a/core/java/android/net/INetworkStatsSession.aidl b/core/java/android/net/INetworkStatsSession.aidl
index f13f2cb664..dfedf6633d 100644
--- a/core/java/android/net/INetworkStatsSession.aidl
+++ b/core/java/android/net/INetworkStatsSession.aidl
@@ -33,7 +33,17 @@ interface INetworkStatsSession {
     @UnsupportedAppUsage
     NetworkStatsHistory getHistoryForNetwork(in NetworkTemplate template, int fields);
 
-    /** Return network layer usage summary per UID for traffic that matches template. */
+    /**
+     * Return network layer usage summary per UID for traffic that matches template.
+     *
+     * <p>The resulting {@code NetworkStats#getElapsedRealtime()} contains time delta between
+     * {@code start} and {@code end}.
+     *
+     * @param template - a predicate to filter netstats.
+     * @param start - start of the range, timestamp in milliseconds since the epoch.
+     * @param end - end of the range, timestamp in milliseconds since the epoch.
+     * @param includeTags - includes data usage tags if true.
+     */
     @UnsupportedAppUsage
     NetworkStats getSummaryForAllUid(in NetworkTemplate template, long start, long end, boolean includeTags);
     /** Return historical network layer stats for specific UID traffic that matches template. */
diff --git a/core/java/android/net/NetworkStats.java b/core/java/android/net/NetworkStats.java
index 46c83df96b..c7ffc19338 100644
--- a/core/java/android/net/NetworkStats.java
+++ b/core/java/android/net/NetworkStats.java
@@ -220,8 +220,10 @@ public final class NetworkStats implements Parcelable {
     // TODO: move fields to "mVariable" notation
 
     /**
-     * {@link SystemClock#elapsedRealtime()} timestamp when this data was
+     * {@link SystemClock#elapsedRealtime()} timestamp in milliseconds when this data was
      * generated.
+     * It's a timestamps delta when {@link #subtract()},
+     * {@code INetworkStatsSession#getSummaryForAllUid()} methods are used.
      */
     private long elapsedRealtime;
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
diff --git a/core/java/android/net/NetworkStatsHistory.java b/core/java/android/net/NetworkStatsHistory.java
index f41306301d..a875e1ad45 100644
--- a/core/java/android/net/NetworkStatsHistory.java
+++ b/core/java/android/net/NetworkStatsHistory.java
@@ -526,6 +526,13 @@ public class NetworkStatsHistory implements Parcelable {
     /**
      * Return interpolated data usage across the requested range. Interpolates
      * across buckets, so values may be rounded slightly.
+     *
+     * <p>If the active bucket is not completed yet, it returns the proportional value of it
+     * based on its duration and the {@code end} param.
+     *
+     * @param start - start of the range, timestamp in milliseconds since the epoch.
+     * @param end - end of the range, timestamp in milliseconds since the epoch.
+     * @param recycle - entry instance for performance, could be null.
      */
     @UnsupportedAppUsage
     public Entry getValues(long start, long end, Entry recycle) {
@@ -535,6 +542,11 @@ public class NetworkStatsHistory implements Parcelable {
     /**
      * Return interpolated data usage across the requested range. Interpolates
      * across buckets, so values may be rounded slightly.
+     *
+     * @param start - start of the range, timestamp in milliseconds since the epoch.
+     * @param end - end of the range, timestamp in milliseconds since the epoch.
+     * @param now - current timestamp in milliseconds since the epoch (wall clock).
+     * @param recycle - entry instance for performance, could be null.
      */
     @UnsupportedAppUsage
     public Entry getValues(long start, long end, long now, Entry recycle) {
diff --git a/services/core/java/com/android/server/net/NetworkStatsCollection.java b/services/core/java/com/android/server/net/NetworkStatsCollection.java
index df372b1459..213ea402f5 100644
--- a/services/core/java/com/android/server/net/NetworkStatsCollection.java
+++ b/services/core/java/com/android/server/net/NetworkStatsCollection.java
@@ -59,16 +59,15 @@ import com.android.internal.util.FastDataOutput;
 import com.android.internal.util.FileRotator;
 import com.android.internal.util.IndentingPrintWriter;
 
-import libcore.io.IoUtils;
-
 import com.google.android.collect.Lists;
 import com.google.android.collect.Maps;
 
+import libcore.io.IoUtils;
+
 import java.io.BufferedInputStream;
 import java.io.DataInput;
 import java.io.DataInputStream;
 import java.io.DataOutput;
-import java.io.DataOutputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -335,7 +334,13 @@ public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.W
 
     /**
      * Summarize all {@link NetworkStatsHistory} in this collection which match
-     * the requested parameters.
+     * the requested parameters across the requested range.
+     *
+     * @param template - a predicate for filtering netstats.
+     * @param start - start of the range, timestamp in milliseconds since the epoch.
+     * @param end - end of the range, timestamp in milliseconds since the epoch.
+     * @param accessLevel - caller access level.
+     * @param callerUid - caller UID.
      */
     public NetworkStats getSummary(NetworkTemplate template, long start, long end,
             @NetworkStatsAccess.Level int accessLevel, int callerUid) {