YSK: Subscriber count on communities only show the numbers of users subscribed from your specific instance. The real number might be much larger than you think.
Edit: Why YSK: New users of Lemmy can find the number low and think that a community is dead or inactive, when infact it might be a thriving place with a lot of activity.
For upvotes it only shows upvotes from the instances your home instance is federated with, so for a smaller instance there's a chance it has not the same big federation list as some more popular instances and thus show smaller upvote count.
Upvotes should propagate across instances. With the current state of everything, not the least of which being congested servers across the ‘verse, it’s a bit of a crapshoot right now.