Edit: My guess was completely wrong, so I just deleted it to help limit misinformation. Check the reply to this comment for a lot better insight.

Don't quote me, but I'm under the impression that dominion is like the final storage for the numbers once they've been ran through a tabulator and used to send those numbers to the main system/send them to be announced.

Imagine it like a bank account. No matter how you add money to the account, (check, cash, coins) it just adds up to your banking balance. Dominion is there to check the balance and tell what it is, the problem is its compromised and people can just add as much money as they want by changing numbers without any oversight.