Settings-> user tags -> track votes

It means you’ve previously upvoted/ downvoted that specific user

i highlated it incase people need to know which I’m talking about and which is the tag

I could be wrong, but this could be Voyager’s vote tracking system? In which case the +1 would indicate that at some point in the past you’ve upvoted one of their posts or replies

How many upvotes you’ve given that user