A scaling point limit, quite simply, is the use of a limit that is affected by the previous cards played. Here's an example where the base limit is 1000 and the absolute limit is 100000.
Player 1: *plays 50-point-card* (Limit begins at 1000)
Player 2: *plays pre-existing 8000-point card* (Limit rises to 8800)
Player 1: *makes an 8500-point card and plays it* (Limit rises to 9680)
Player 2: *plays card that says to take cards out of the suck box*
Player 1: *plays 400-point-card*
Player 2: *plays 500000-point-card from the suck box* (limit rises to 100000)