diff --git a/inc/Maat_command.h b/inc/Maat_command.h
index 202098f..0a65beb 100644
--- a/inc/Maat_command.h
+++ b/inc/Maat_command.h
@@ -131,7 +131,7 @@ void Maat_add_region2cmd(struct Maat_cmd_t* cmd,int which_group,const struct Maa
 
 void Maat_free_cmd(struct Maat_cmd_t* cmd);
 int Maat_format_cmd(struct Maat_cmd_t* cmd, char* buffer, int size);
-// REGION_EXPR and REGION_SIMILARITY need to escape input string.
+//Input string of REGION_EXPR and REGION_SIMILARITY need to be escapeed.
 char* Maat_str_escape(char* dst,int size,const char*src);
 
 //Deletion failed due to not complete synchronize with Redis.
diff --git a/inc/Maat_rule.h b/inc/Maat_rule.h
index ffda39b..b4d3ca9 100644
--- a/inc/Maat_rule.h
+++ b/inc/Maat_rule.h
@@ -152,7 +152,7 @@ enum MAAT_INIT_OPT
 	MAAT_OPT_REDIS_INDEX,			//VALUE is interger *, 0~15, SIZE=sizeof(int). DEFAULT: 0.
 	MAAT_OPT_CMD_AUTO_NUMBERING,		//VALUE is interger *, 1 or 0, SIZE=sizeof(int). DEFAULT: 1.
 	MAAT_OPT_DEFERRED_LOAD,			//VALUE is  NULL,SIZE is 0.  Default: Deffered initialization OFF.
-	MAAT_OPT_CUMULATIVE_UPDATE_OFF	//VALUE is  NULL,SIZE is 0.  Default: CUMMULATIVE UPDATE OFF.
+	MAAT_OPT_CUMULATIVE_UPDATE_OFF	//VALUE is  NULL,SIZE is 0.  Default: CUMMULATIVE UPDATE ON.
 };
 //return -1 if failed, return 0 on success;
 int Maat_set_feather_opt(Maat_feather_t feather,enum MAAT_INIT_OPT  type,const void* value,int size);
diff --git a/tools/digest_gen.c b/tools/digest_gen.c
index f195e27..c830229 100644
--- a/tools/digest_gen.c
+++ b/tools/digest_gen.c
@@ -84,6 +84,7 @@ void digest_gen_print_usage(void)
 {
 	printf("digest_gen dermines the similarity of two signatures/strings/files with a score in [0,100].\n");
 	printf("Higher score means more similar.\nUsage:\n");
+	printf("\t-h print this specification.\n");
 	printf("\t-f [FILE], caculate a file's SFH digest.\n");
 	printf("\t-s specify the first string/file for comparing.\n");
 	printf("\t-d specify the second string/file for comparing.\n");