Tipping out 2% to bussers-not via tips but via total sales

As I was getting cashed out I saw my credit tips were 38.74 and my manager subtracted my tip outs which was written x2% and my tip out was a whopping 17 dollars. She then told me it’s from my total sales which was $888. I’ve worked at 4 other restaurants and I’ve never tipped out this way before. Any of you tip out based on total sales?