Pretty simple: 6 minutes is the minimum default for time tracking in my realm, per contract. Clients don't want multiple entries for 30 seconds or 2 minutes here and there - instead, we report in 10th's of an hour.

I quite often fix bugs in 2 or 3 minutes, or even less - on separate tasks/projects.

However the minimum time allotment for these things (billing) is 6 minutes. All time tracking (per contract) is rounded up to the next 6-minute (1/10th of an hour) interval.