first the block should have the cast mark V90HM6015AA as well as 200 cast on it

the bore standards are
STANDARD CLASS 2 MM 90.810 TO 90.820
STANDARD CLASS 3 MM 90.820 TO 90.830

the cylinder class at original manufacture boring is found as a row of 4 numbers stamped in a line anoting clys 1 to 4 located an the flat section of casting between the dizzy hole and the block.

normaly there all the same either class 2 or 3 but you can get a mixture.

if the block was new then were you are taking the measurement with the vernier would be fairly acurate (but best to use a bore measurement tool with a dial gauge) however if the block is any way worn then its a case what oversize to bore to and that will depend on the max wear at the top of the piston ring travel. any good engineering shop can do all the measurement and assessment if your going this route