[Majingir]

^Don't think that thing applies until the final 10 seconds of a period though since you can obviously hear the sound effect counting down the final 10 seconds,each going off every second.

Here's the numbers I got. For every 10 seconds in real life,here's how much time passes on the game clock if you set the period length to each of the following:

5 minutes:55 seconds(should be 40 seconds)
10 minutes:30 seconds(should be 20 seconds)
15 minutes:20 seconds(should be 13 seconds,I believe I did math right for this one...)
20 minutes:14 seconds(should obviously be 10 seconds)

Meaning:
5 min periods are actually 3.6 minutes
10 min periods are actually 6.7 minutes
15 min periods are actually 10 minutes
20 min periods are actually 14.3 minutes