Need to reinstall - which version?

I’ve hosed up my OpenVPN while trying to implement the VPN button capability on my GL-AR300M. I want to re-install the firmware, but I can’t find a guide to the different versions: /nand , v1, etc. I downloaded the v1 .bin file, but the router says that it’s not the correct version for my router, so please tell me which one to use.

http://www.gl-inet.com/firmware/ar300m/nand/v1/

The above is the correct firmware for Nand.