diff --git a/README.md b/README.md
index a62ea35..06bcb13 100644
--- a/README.md
+++ b/README.md
@@ -207,7 +207,7 @@ long (`*`) | a long option (e.g. `--ghq`)
 desc | a description for the option
 func (`*`) | a command which returns directory list (e.g. `ghq list --full-path`)
 condition | a command which determine that the option should be implemented or not (e.g. `which ghq`)
-format | a string which indicates how to format selected line by the filter before passing cd command. `%` will be replaced as a selected line (e.g. `$HOME/src/%`)
+format | a string which indicates how to format a line selected by the filter before passing cd command. `%` is replaced as a selected line and then passed to cd command (e.g. `$HOME/src/%`). This is useful for the case that input sources for the interactive filter are not a full-path.
 
 > **Note**: `*`: A required key. But either `short` or `long` is good enough.