Strength increases the Carry weight by 15% for each LVL. but dupes do not carry 15% more instead 15Kg more. so a dupe that should have +105% carry weight will instead carry 105Kg more. I don't know which of those 2 values are supposed to be right but that's what's going on.
1. Start a new game. 2. select a dupe with points in strength. 3. let the dupe carry an item by sweeping. 4. check values