1. the benchmark shows how much RAM you have on the GPU?
2. If you have the 2GB version, then it is normal. It is 1GB per card, 2GB total.
3. If you had a previous Nvidia card on the same computer, you need to download specialized driver cleaning software (ie. drive sweeper) to get rid off all the Nvidia driver info. (regular uninstall doesn't remove stuff deep in the registry, etc)