No you can't get 64K out of a 2.0 cuft softener with regular mesh resin. The max is 60K and that requires 30 lbs/regeneration. And that gets you very poor salt efficiency.
Who ever you bought the softener from should have told you how to program it. They should have sized it for you too.
I see you said back in the beginning of Mar that you installed it then. With 84 gpg you should have bought a larger softener.
Who did you buy it from?
How do you have it programmed now?