diff --git a/cmd/cmd_bucket.go b/cmd/cmd_bucket.go
index 42e69ac..fa8c6a2 100644
--- a/cmd/cmd_bucket.go
+++ b/cmd/cmd_bucket.go
@@ -42,7 +42,7 @@ $ gnfd-cmd bucket create --visibility=public-read  gnfd://gnfd-bucket`,
 			&cli.Uint64Flag{
 				Name:  chargeQuotaFlag,
 				Value: 0,
-				Usage: "indicate the read quota info of the bucket",
+				Usage: "indicate the read quota info of the bucket. charged quota defines the read data that users are charged for, measured in bytes.",
 			},
 			&cli.GenericFlag{
 				Name: visibilityFlag,
@@ -79,7 +79,7 @@ $ gnfd-cmd bucket update --visibility=public-read --paymentAddress xx  gnfd://gn
 			},
 			&cli.Uint64Flag{
 				Name:  chargeQuotaFlag,
-				Usage: "indicate the read quota info of the bucket",
+				Usage: "indicate the read quota info of the bucket. charged quota defines the read data that users are charged for, measured in bytes.",
 			},
 			&cli.GenericFlag{
 				Name: visibilityFlag,
diff --git a/cmd/cmd_payment.go b/cmd/cmd_payment.go
index 7bdd81d..7f5b551 100644
--- a/cmd/cmd_payment.go
+++ b/cmd/cmd_payment.go
@@ -25,7 +25,7 @@ $ gnfd-cmd payment buy-quota  --chargedQuota 1000000  gnfd://bucket-name`,
 		Flags: []cli.Flag{
 			&cli.Uint64Flag{
 				Name:     chargeQuotaFlag,
-				Usage:    "indicate the target quota to be set for the bucket",
+				Usage:    "indicate the target quota to be set for the bucket. charged quota defines the read data that users are charged for, measured in bytes.",
 				Required: true,
 			},
 		},