Monthly active user data unserstanding
We are trying to calculate our MAU, and for that, we are considering unique visitors and filtering it with "excluding 1st visit" segment:

However, I'm seeing a different number when I look a single month and with many months:
Feb only

January until today

The Feb values are different when looking at the month alone and looking at it with other months included. Why?
If I don't use the segment, this difference doesn't happen.
Thanks in advance
