When boxers cut weight and re-hydrate after

I've always wonder about this, but when boxers cut weight and re-hydrate after, how much does each pound they need to cut equal to in terms of re-hydrate pounds afterwards? Like I heard every pound of weight equals to 5 lbs of re-hydration. So 147 lbs = 165 lbs and 146 lbs = 160 lbs That's one of the reasons why catch-weights are always tricky