diff --git a/fdbclient/Knobs.cpp b/fdbclient/Knobs.cpp
index 14686c0e38..290bb06cf1 100644
--- a/fdbclient/Knobs.cpp
+++ b/fdbclient/Knobs.cpp
@@ -66,7 +66,7 @@ void ClientKnobs::initialize(bool randomize) {
 	init( RESOURCE_CONSTRAINED_MAX_BACKOFF,       30.0 );
 	init( PROXY_COMMIT_OVERHEAD_BYTES,              23 ); //The size of serializing 7 tags (3 primary, 3 remote, 1 log router) + 2 for the tag length
 	init( DEFAULT_SMOOTH_AMOUNT,                   5.0 );
-	init( INIT_MEAN_SHARD_BYTES,                 16384 );
+	init( INIT_MEAN_SHARD_BYTES,                200000 ); if( randomize && BUGGIFY ) INIT_MEAN_SHARD_BYTES = 40000; // The same value as SERVER_KNOBS->MIN_SHARD_BYTES
 
 	init( TRANSACTION_SIZE_LIMIT,                  1e7 );
 	init( KEY_SIZE_LIMIT,                          1e4 );
@@ -231,6 +231,7 @@ void ClientKnobs::initialize(bool randomize) {
 	init( MAX_TAGS_PER_TRANSACTION,                   5 );
 	init( MAX_TRANSACTION_TAG_LENGTH,                16 );
 	init( COMMIT_SAMPLE_BYTE,                     65536 );
+	init( INCOMPLETE_SHARD_PLUS,                   4096 );
 	init( READ_TAG_SAMPLE_RATE,                    0.01 ); if( randomize && BUGGIFY ) READ_TAG_SAMPLE_RATE = 1.0; // Communicated to clients from cluster
 	init( TAG_THROTTLE_SMOOTHING_WINDOW,            2.0 );
 	init( TAG_THROTTLE_RECHECK_INTERVAL,            5.0 ); if( randomize && BUGGIFY ) TAG_THROTTLE_RECHECK_INTERVAL = 0.0;
diff --git a/fdbclient/Knobs.h b/fdbclient/Knobs.h
index ee1f447760..a9b03f3e58 100644
--- a/fdbclient/Knobs.h
+++ b/fdbclient/Knobs.h
@@ -217,7 +217,8 @@ public:
 	// transaction tags
 	int MAX_TRANSACTION_TAG_LENGTH;
 	int MAX_TAGS_PER_TRANSACTION;
-	int COMMIT_SAMPLE_BYTE;
+	int COMMIT_SAMPLE_BYTE; // The expectation of sampling is every COMMIT_SAMPLE_BYTE sample once
+	int INCOMPLETE_SHARD_PLUS; // The size of (possible) incomplete shard when estimate clear range
 	double READ_TAG_SAMPLE_RATE; // Communicated to clients from cluster
 	double TAG_THROTTLE_SMOOTHING_WINDOW;
 	double TAG_THROTTLE_RECHECK_INTERVAL;
diff --git a/fdbclient/NativeAPI.actor.cpp b/fdbclient/NativeAPI.actor.cpp
index 46500eb81b..2a832a0bf6 100644
--- a/fdbclient/NativeAPI.actor.cpp
+++ b/fdbclient/NativeAPI.actor.cpp
@@ -3329,7 +3329,9 @@ ACTOR Future<Optional<ClientTrCommitCostEstimation>> estimateCommitCosts(Transac
 				std::vector<pair<KeyRange, Reference<LocationInfo>>> locations =
 				    wait(getKeyRangeLocations(self->getDatabase(), keyRange, CLIENT_KNOBS->TOO_MANY, false,
 				                              &StorageServerInterface::getShardState, self->info));
-				uint64_t bytes = locations.size() * self->getDatabase()->smoothAvgShardSize.smoothTotal();
+				if (locations.empty()) continue;
+				uint64_t bytes = CLIENT_KNOBS->INCOMPLETE_SHARD_PLUS +
+				                 (locations.size() - 1) * self->getDatabase()->smoothAvgShardSize.smoothTotal();
 				trCommitCosts.clearIdxBytes.emplace(i, bytes);
 				trCommitCosts.writtenBytes += bytes;
 			}