There is nothing incorrect, if we take your values 26mhs for stock gtx 1070 and probable 43mhs stock rtx 2070 then we target 26 to 32, that gives almost 30% overclocking for the gtx 1070, if we do the same taking your value for stock rtx 2070 43 and throw 30% 43 + 13 = 56mhs. I have no idea why you said my calculation is incorrect cause your calculation is a reflection of what i said.