Wow, I see, but you are wrong too, at least you should edit the last column as left/ available smerits. That column does not present all smerits one user (in the list) earn each month.
In fact, it presents:

Total earned smerits - total sent-smerits ~ total left/ available smerits (till the end day of July).

The list still should be sorted by total earned merits of total earned smerits (they are the same in ranking), rather than total left/available smerits, in my opinion. Because they are indicators of good works users did to earn merit & smerits; the left/ available smerits does not represent their works, or less representative.

The level of active contributions should be measure through:
- Total merits earned: more merits earned, likely more contributions to the forum (if not abuse merits).
- Total smerits sent: actively help other good users or not.