You normally don't enter anything directly into the Record Deposits.  You should either use Customers > Receive Payments (if there's an invoice) or Customers > Enter Sales Receipts (if there isn't an invoice).  This will group the payments into Undeposited Funds.  When you're ready to actually go to the bank and make the deposit, go to Banking > Make Deposits and select the payments you're depositing. 

You can enter additional lines to the Make Deposits screen, but this would normally only occur if you received a non-customer check like a refund from a vendor.  In this case, you'd use the expense account you used on the bill, check or credit card charge you previously entered (since a refund check reduces your expenses).