Could someone enlighten me on the PBs and Ashes?

This month I scored 2 PBs, then another 1, then today another 3. 4 different ones in total.
2 of the original PBs ones were bested today, and the tags ("PB") disappeared from the previous session.

A conclusion : Anyone can have, at the best, 6 PBs at any time, and also in any month.

So a person can break his/her own records many times in any month, and only 6 can be counted for the Ashes (?).

And what happens if I break all six on the 1st of the next month?
The tags will all disappear from the previous month.