On zero turn mowers tire pressure is critical
1 psi off side-to-side will affect cut quality and so will a bunch of other things
measure at the blade, it's what does the cutting. Some measure at the deck but the deck shell doesn't cut grass and sometimes there is some difference in the shape of the deck shell such that leveling the shell itself won't level the blade cut. Deere is notorious for this. Bad Boy as well but Bad Boy decks are usually mostly "square", well they are when they're new. The 60" decks (especially the ZT/CZT) was made in a way that they bend kind of easy even though they're 1/4" thick steel. Don't see it with the naked eye but they get impossible to level, and you'll fight yourself for hours if you let it, and don't see the bent deck shell.
G1800/1900/G2000 aren't any easier since the rear wheels ride the ground all the time, which is what sets the deck level. Often have to use a washer under some of the gauge wheel mounts to space them out/up/down to adjust the level a little.
On the bx's the front hanger can get stuck and they're no fun to get them unstuck. Loosen the jam nuts while the front hanger is installed, then remove the front mounts so that you can adjust. Lots easier to do it under the tractor than even in a vise. Set the side-to-side to zero or very close to it THEN adjust front-to-rear using the hanger only. Once you get that close re-measure side-to-side again, it should be very close if not still spot on. But if you have to adjust the hanger a lot, it can affect the side-to-side adjustment a little too and then you're splitting hairs and exercising your own self patience.
You will not likely see 1/16" off, that's only .0625" so just get it within 1/16 and it'll be fine
I'm real picky and like to see it at zero even though I can't see 1/16" and nobody else can either. Just OCD and it shows in how long it takes to adjust a deck!