Well you just need to do some basic math. 12% of 60fps is 7.2fps.
But whatever gave you 12% is not a matter of fact, it is guesswork at best. Each game is different and different settings will give you a different amount of bottleneck.
With that being said, I think the GTX 1050 Ti is the most I would pair with an old Phenom X4 even if it does bottleneck.