If you live near an office and go in above and beyond the three days 8 hours a day requirement- say working a half day in office on day 4 - this will actually hurt you. The calculation is looking at average hours in office per day so a half day will lower your average. So there's no point in going in unless you plan to spend the full day
Additionally,if you take a half day PTO and then go in the office the second half of that day, this will also hurt your average. A half day of PTO is considered a full day in office so do not go in beyond that.
Its a combination of badge swipes and connection to office network.
Average is currently calculated on a 4 week basis but the intention is to ramp up to a 13 week average.