When you go to the "Current Accounts" section of your Invvest account, you benefit from 3 views:
Current Balance
Credit
Net Balance (or effective balance)
Current Balance
The current balance is the gross amount you hold across all the bank accounts added to Invvest.
Credit
Credit is the amount you owe to the bank. This amount is always negative and includes your overdrawn accounts and the amounts due on your credit cards.
Net Balance
The effective balance is the net amount you hold across all the bank accounts added to Invvest. It is simply your current balance minus the "Credit" portion you owe to the bank.