https://www.youtube.com/watch?v=WnrFaH3F3Ks&t=402s

Recently bought the Magic Tool Stacker and there is a feature that only appears on the written instructions that refers to a "rebate" on the tool. On Petitjean's promotional YOUTUBE above, he refers to the "rebate" (see 10:00 mark) but only spends less than 2 seconds on its application. Can someone explain its use when stacking material? Thanks.