The rates that you see when you're logged into your account as a Plus member will include an exclusive cashback bonus. This bonus will be added as transactions track to your account, so they will immediately show as the higher rate on your Earnings page.
After you have made a transaction, if you go to your cashback by date page then you will also notice a 'Top-Up' column on this page where you are able to see exactly how much this bonus was added on for.
« TopCashback FAQ's and Help Overview