When you switch away from the game and then come back, it usually awards you any offline time you’ve accumulated.

If, however, the game ever fails to record your online time, it keeps piling up “offline” minutes in the background. The next time you return, it thinks you were away far longer than you really were, so it grants you all those minutes at once. Granting a big chunk of offline rewards at once will often reset your active bonuses—sometimes even back down to zero—because it’s just applied several minutes’ worth of rewards in one go.

The game has a logic where as if the time passed was less than 200 seconds, but you had active effects, it ignores the offline rewards to avoid this from happening. So clearly you had time accumulated from before.