Unfortunately that doesn’t mean 6% of As overestimated, it means ~40% of As overestimated. CAGs have given 13.8% of all grades an A when only 7.8 (compared to 2019) should have got them, so 6 out of 13.8 were overestimated which is around 40%. So that 40% of A grades will drop down to an A.
The A grades are also overestimated. With the 6% from A* dropped down to an A that takes up 6 of the 17.7% to be allocated so only 11.7% left for the 24% of CAG A grades to have, so ~ 12/24 will drop down to a B or 50% of them.
The B grades are also overestimated. With the 12% from A dropped down to a B, that takes up 12 of the 26% to be allocated so only 14% is left for the 27% of CAG B grades to have so ~ 13/27 will drop down to a C so 48% of them. Then similarly for the C grades etc, though in a lower proportion.
The overestimating by schools is worse than the % figures seem to suggest, sadly.