I've seen that this was "fixed" in Hotfix 29.0.2, but it seems to have re-emerged. I fully ranked it to rank 3 in one go, so not sure if the display bug is only in the mod fusion screen, or if it stays in other UI elements after upgrading to Rank 2. For comparison, Rank 1 and 3 showed exact 20% and 40% values, respectively.