Because of the 6th spot where the person is waiting there is a line of grey boxes across the sheet pre filled out for them as waiting in a diagonal. When you then go from 6 to a full 5 the some of the lines are not filled out vertical and you need to jump forward 5 targets. It's a bit difficult to explain, it's not easy even when you look at the sheet. The easiest way we found was to actually still shoot as a 6 and leave the missing persons cage empty, problems came when the ref thought they could manage as a normal 5, then found out they couldn't.