Why do some reviewed transactions show as added and some show as matched,

Hi there, @contact37.

It'll show Added if the transactions are added from the For Review tab or if you've created a new record. Then, it'll show matched if QuickBooks finds any records you've already entered in your QuickBooks Online (QBO) account.

I've got you this great article for more information: Download, Match, and Categorise your Bank Transactions in QuickBooks Online.

Also, here's an article that can help guide you in reconciling your accounts: Reconcile Accounts.

Keep me posted if you need further assistance. I'm always here to help.