This is year-on-year for Q1. If I want whatever Macs I bought in Q1 '24 to net out neutral here, I need to have bought an equal number of Macs in Q1 '23.
Per a sibling commenter, Apple did still sell Intel Macs throughout Q1 '23, so it's possible for the earlier set to have been Intel and the later to have been M-series, which we could count as the upgrades you describe. Intuitively it seems difficult to imagine very many people would have done this, but to set an upper bound we would need M-series vs. Intel share figures for Q1 '23.
