I'm also curious to see someone else with the full picture but I have one partial answer
The ones with 0 just aren't on pathofexile-discuss.com's allowed list: https://pathofexile-discuss.com/instances
No idea why the others are out of sync. Maybe the pathofexile instance added the other instances to the allowed list at different times?
Two on Lemmy. One on lemmy.world because it seemed both popular and stable enough, and a second one that I'm planning to use now that Beehaw blocked lemmy.world.
Feeling really bummed out that posts on communities from Beehaw are now different depending on what instance you use to view them now.