diff --git a/optimize.sh b/optimize.sh
index f9dad52..d261f23 100755
--- a/optimize.sh
+++ b/optimize.sh
@@ -32,7 +32,8 @@ _help() {
     echo "       -q, --quiet ..... run image optimization quietly"
     echo " Other options :"
     echo "       -h, --help, help ... displays this help information"
-    echo "       --cmin <n> ... File's status was last changed n minutes ago."
+    echo "       --cmin [+|-]<n> ... File's status was last changed n minutes ago."
+    echo "         act find cmin argument (+n : greater than n, -n : less than n, n : exactly n)"
     echo "Examples:"
     echo "  optimize all jpg images in /var/www/images"
     echo "    img-optimize --jpg /var/www/images"