Monthly Data Quota - Gargoyle?

I’m hoping to set a total monthly upload/download quota for all traffic passing through the AR300m. There don’t appear to be any options to do this using OpenWRT, Does anybody have experience installing Gargoyle on the AR300m? this seems to be the only option to set up monthly quotas.

Gargoyle Seems very old and there is not too many models supported.

The only Gargoyle supported model from us is GL-AR150