Add comment about ulimit format.
Fixes
@@ -2399,6 +2399,9 @@ available in the default container, you can set these using the `--ulimit` flag.
> In other words, the following script is not supported:
> `$ docker run -it --ulimit as=1024 fedora /bin/bash`
+The values are sent to the appropriate `syscall` as they are set.
+Docker doesn't perform any byte conversion. Take this into account when setting the values.
+
## save
Usage: docker save [OPTIONS] IMAGE [IMAGE...]
