You're measuring the very top edge of the bore .
That's the part that rarely wears any at all .
Much better to take measurements incrementally down through the complete bore .
Like at the 1/4 , then 1/2 and 3/4 down .
Normally the bore will be a touch larger at the bottom .
You can do the same on the piston .
By the time you're done , you'll know the piston to bore clearance ( important information ) .
If you install new ring(s) , be sure to hone in a decent crosshatch or the new will not seat .