It says I got the 3 gb and 6 gb version ( I got a prebuilt)

Solution
Looks like info from system requirements lab which is notoriously bad at reporting vram on GPUs that have models with different amounts of vram. Run a better utility like gpuz to see how much vram you have.

USAFRet

Titan
Moderator


And what, exactly, is telling you "8GB"?