"Today, PlayStation revealed that its PS5 has sold 40 million units. Microsoft doesn’t share hardware numbers typically, but court documents, math, and slides from an ID@Xbox in Brazil seem to suggest the Xbox Series X|S line-up is around 20-23 million units sold globally. That essentially puts the PS5 at a 2:1 advantage against Xbox, but perhaps the split is even worse than that beneath the surface. "
They’re just following the naming convention established by Windows: 1, 2, 3, NT, 95, 98, 2000, Me, XP, Vista, 7, 8, 10, 11