I saw a discussion stating 4 minutes as the offline time(without bonus). That's incorrect cause you only get 4 minutes competing online.
Regardless, the most I've hit has been 22, where you get 3 minutes for offline. Including bonus, it's 52. Now if you switch over to arcade mode, then the most I hit has been 113 in the first round. 113 in 3 minutes plus the bonus.
For any who doubt, you can probably find me on discord, and I'll gladly send screenshots