tyalpha: better documentation

man/terminology-helpers.1

@@ -10,7 +10,9 @@ List directory contents with bells and whistles
 .
 .TP
 .B tyalpha [-h][-p] on|off|<opacity level>
-Set transparency level of the background
+Set transparency level of the background.
+
+<opacity> is between 0 and 100.
 .
 .TP
 .B tybg [-h] [-p] [FILE1 FILE2 ...]

src/bin/tyalpha.c

@@ -14,6 +14,8 @@ print_usage(const char *argv0)
           "  Change the terminal transparency on or off\n"
           "  -p  Make change permanent (stored in config)\n"
           HELP_ARGUMENT_DOC"\n"
+          "\n"
+          "<opacity> is between 0 and 100\n"
           "\n",
           argv0);
 }