So with vommunities the only instance that has a full count of all subs is the host. As an example if i want to know an accurate count of how many people subscribe to !technology@lemmy.ml i need to open lemmy.ml, click communities, and choose technology. The sub count on any other instance for that community will only show how many on that server are subscribed. To put this in real terms lemmy.ml says its technology community has 14.7k subs. Now my instance monero.town says that same community has 3 subscribers. That only means that 3 people from monero.town sub to !technology@lemmy.ml
Hope that makes sense