I thought It was actually ((ATK/(DEF+1))+1, bascially to rule out a 0 divisor (in case of ef going to 0 by debuffs or whatever I guess) and a log10(0). So it’s if my example had 999 as divisor +1 = 1000. But let me check damage formula again, I might remember it wrong.
EDIT: @Delcas You’re right, they didn’t put that extra parenthesis I’m using on the divisor. If that’s the correct formula, it’d get weird if def went to 0, as the whole factor would tend towards positive infinite.