If the pot is $280, the RAISE has to be $280, not the bet. As $60 of the 4 bet goes to calling the 3 bet, it would take a $340 bet to make a $280 raise.
When talking about bet sizes as a percentage of the pot, it’s actually always the raise size that is being measured, not the total bet. If we were measuring the total bet, then a $0 raise wouldn’t be 0% pot.