Bridge & your devices · Collab Sync
Why does Collab Sync ask me to confirm a large folder?
Short answer: A big folder means copying all of it to the other Mac, so Collab Sync shows its size and file count and asks you to tick “Sync it anyway” first. Choose a smaller subfolder if that's more than you meant.
Because mirroring a big folder copies all of it to the other Mac, Collab Sync makes sure you meant it. Its review shows the size and file count, and for a large folder you tick This is a large folder (…). Sync it anyway. before you can go on.
If that's more than you wanted, choose a smaller subfolder instead.