@woll it looks like you have counted correctly.
Mate positions where the mating side has lost their King still count

Entries for Weekly Challenge 180 has closed. Thanks to all users who participated.

The winner is @woll who demonstrated it is possible to have 24 mate positions in the same Antichess game in the following study: playstrategy.org/study/qdXDAvRu/dKaffG0r

Users are still welcome to attempt this challenge and post answers here, but the winner has been fixed. The next challenge can be found here: playstrategy.org/forum/weekly-challenges/weekly-challenge-181-diagonal-action