It looks like the scoring takes one's top 20 scores over the period (2019-2021) WARCA has been ranking contesters. One can forgo whichever contests they want to and eventually accumulate 20 'tests, although there may be a score reduction like so:
"Ranking
Up to 20 contests can be credited to get ranking points. Contests ended within last 24 months give 100 percent of points, from 24 to 36 months – 75 percent, 36 to 48 months – 50 percent."
No more than 50 percent of credited contest entries can be of the same mode (CW, PHONE, DIGITAL). All sort of digital modes considered as one. Mixed mode contests (irrespective of the mode used by a participant) can be counted as either mode.
Score calculation
All stations are (initially) created equal. All of them are on the surface of Earth, and WARCA points are independent of countries, continents, zones or other artificial parameters. Exact formula for score calculation is in the separate document."
QTH Locators
We are asking to be very precise with the QTH locators associated with the calls. Since WARCA score calculations are based on comparison of scores within geographic areas..."