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.

The above is the correct firmware for Nand.