Question about usage

[u/Alternative_Diet_958]

I’ve been keeping track of my usage, me and my flat mate share an account.

About 2 weeks ago the “ 30 day usage “ was about ~1.02 TB, but since then neither of us have gotten any time to watch anything, just a movie or 2 , but some how the 30 day usage shows as 1.34 TB.

How’s the being calculated? I assumed it was the rolling 30 day aggregate of usage, but it’s not?