diff --git a/tsmark/__init__.py b/tsmark/__init__.py
index 9818552..397d54a 100644
--- a/tsmark/__init__.py
+++ b/tsmark/__init__.py
@@ -13,7 +13,7 @@ def get_options():
         dest="timestamps",
         default=None,
         required=False,
-        help="Comma separated list of predefined timestamps, in frame numbers, or HH:MM:SS.FF. You can use the -o  output file as input via --ts $( cut -d, -f1 ts.csv | xargs printf '%%s,' )",
+        help="Comma separated list of predefined timestamps, in seconds, or HH:MM:SS.ss. You can use the -o output file as input via --ts $( cut -d, -f1 ts.csv | xargs printf '%%s,' )",
     )
     parser.add_argument(
         "-o",