A portion of my data did not get charged last night. Steam was still able to access other servers, even though I was using Steam-Limiter. I had it set to Orcon only. I think Steam may have been using http to download from other servers. From my router logs I could see that the only thing running on port 27030 was the Orcon server.
I really wish there were a setting in Steam that would force it to use your preferred server only.