So when i add an melee atk it calculates BAB+Ability+Size and Str mopdifier. si with BAB 8 and small size and STR mod 3 i would get 15 on ATK. If i want to dumb sdtr and use dex with weapon finesse i can use STR isntead of DEX mod woudnt i lose out on ATK roll since the Abbility is STR so i would hjave +12 instead of 15 if i have DEX +3 mod