https://www.gamespot.com/articles/assassins-creed-odyssey-has-series-best-first-week/1100-6462447/

Assassin's Creed Odyssey is off to a flying start. The latest entry in Ubisoft's blockbuster franchise had the best launch week for the franchise on the current generation of consoles, the French publisher announced in a press release. That means the game had a better first-week performance than the first Assassin's Creed game released for PS4 and Xbox One, Assassin's Creed IV: Black Flag (2013), as well as all the follow-ups including Assassin's Creed Unity (2014), Assassin's Creed Syndicate (2015), and Assassin's Creed Origins (2017).

Ubisoft did not share a specific first-week sales figure for Odyssey, but the company said the milestone includes internal estimates of game sales--digital and physical--as well as revenue from microtransactions (called "player recurring investment" in the press release). In other words, it doesn't necessarily mean Odyssey outsold the aforementioned games on a unit basis.