Reconnecting a previously connected PC to syncthing?

I have what I think is a quick question…

I have a PC that I previously had connected to my “main” syncthing server, but I noticed today that it was no longer syncing. My guess is that I forgot to reconnect this machine when I moved my server to a faster PC.

The folders are still on this PC, but are a couple of months out of date. If I add the new machine to my setup and connect to my “main” server, will I end up with a bunch of duplicate files, or will it only update the files that are missing or different from those on the main server?

If the folder IDs are the same you should be fine.