I don’t know what it comes too in the 3, 4 or 5 cut method, but if you can get to 1/64th over 12” that’s close enough.
Don’t kill your self - this is woodworking!
That said, some has to do with the saw. Not to offend but you’re not dealing with an upper tier machine there.
Adjust blade parallel to miter slots, and back of blade should be .003-.005” wider at back (out feed) of blade to fence.