diff --git a/can/logger.py b/can/logger.py
index 0b73dd785..8cb201987 100644
--- a/can/logger.py
+++ b/can/logger.py
@@ -193,9 +193,10 @@ def main() -> None:
         "--file_size",
         dest="file_size",
         type=int,
-        help="Maximum file size in bytes (or for the case of blf, maximum "
-        "buffer size before compression and flush to file). Rotate log "
-        "file when size threshold is reached.",
+        help="Maximum file size in bytes. Rotate log file when size threshold "
+        "is reached. (The resulting file sizes will be consistent, but are not "
+        "guaranteed to be exactly what is specified here due to the rollover "
+        "conditions being logger implementation specific.)",
         default=None,
     )