How do re-imported tables count towards monthly active rows (MAR)?
When a table is re-imported on the first day of the month, the entire table counts towards your MAR. For all subsequent days that month, only new records count towards your MAR.
A monthly active row is uniquely identified by its primary key. Every time we see a row with that primary key, we know that it is the same row that we already observed that month and do not include it in your MAR.