Assassin's Creed Odyssey, Xbox One:
Ubisoft Connect has 32 hours of playtime and the main menu shows 19 hours. Which of these is true now?
Ubisoft Connect probably also counts the time you spend in the main menu. In the main menu only the time that you have spent in the game. So the time in the main menu is probably more accurate.
I didn't play Odyssey, usually games, when they show the game time, always show the time you spent in the game.
I.e. Something like loading times and in the menu are not included.
Ubisoft Connect shows you the time the game was open.
As far as I know, Ubisoft Connect works across platforms, i.e. If you have played AC Odyssey on another device (e.g. PC), Ubsifit Connect may show both times together (but I don't know, I haven't tested it yet).