How does this leaderboard thing work?

I see the top Cross Country Mare - Isn't even competing in the sport - hasn't nearly the points & winnings as other horses on the list -- and not even as much as my mare - who is competing in the sport - and somehow doesn't make the list.
https://horseeden.com/horse.php

even the bottom of the list - hasn't competed in the sport since March.

so - again -- how does this work that they're both on the Cross Country List?

It's not about competing, it's about production. She probably has stronger XC foals than your mare.

Eventing is all three added up. XC is individual. The mares may be strong in XC but weak in dressage/show jumping, which would take them out of the running for the all discipline leaderboards