the average number of active devices per the past 30 days.
On a daily basis, system computes the number devices that has been active in the past 30 days. Average of the present measure for report period would be MAU.
In other words, MAU is computed using moving 30 days window. For example, if the report is aggregated by days, than MAU for 2021-10-20 would show the number of devices been active between 2021-09-21 and 2021-10-20.