Ernie is correct. There are many servers that are no longer reachable, or are temporarily down. Each time your server tries to connect, and it fails, it increases the count.
If reaching a server errors out long enough, your server will just stop trying to reach it. Self-healing, as it were.
These are background jobs that run on a schedule.
I'm not an expert either, but your numbers pretty much match mine. So, all good.
Don't click any buttons!
Extremely large instances end up fighting these Sidekiq queues and sometimes need extra servers because they back up. But you need an awful lot of accounts before that will become an issue.