How can I tell what % this is

Hey all. Bought a "used" truck with some tint in the front and rear. I know the fronts are far below the 15% I want, but I can't tell what the backs are. Any educated guesses or ways I can easily find out? Gonna be going to a local shop for prime xr plus 15% in the front(rears too possibly I guess), and 55% on the windshield.

I know the hue/tone of it looks different than the xr plus in the wife's car, but I'm no expert.