Adored TV takes AMD's wafer allocation for 2020 and guesses approx how many chips and what kind add up to that amount.
18:00 is where he starts talking specifically about the next gen console APU's.
While he's only guessing, and there's a lot to take into account, he get's quite close to the total by the end, so he's likely not far off.
25:00 is where he talks about XBSX specifically. He uses 56 cu's for it's GPU and ends up around 420mm2 for the APU size.