Heathcare Table, Period 3, Kids going off ACA before Medicare

The second lowest cost silver plan (SLCSP) depends on the number of family members covered. PRC includes the ACA insurance table to allow for differences in numbers of covered family members during Periods 1,2,3, and 4.

Specifically for Period 3 (early retirement), there will initially be four of us on ACA, then three, then two. This is all before Period 4, when I go on Medicare, before my wife. I don't see any way to list the different SLCSP costs during Period 3, when we go from 4 to 3 to 2 covered persons. For now, I just over-estimate it and leave Period 3 as the cost for 4 persons.

Am I understanding this / approaching the problem correctly?

Thanks,

Dave