On the Loan Payment Screen, you want to select the loan you are wanting to discount, Once you have done that you want to enter the full overdue amount, then

Select The Loans to Retail on the Main Menu Screen, Then Select wether you would like to do all Overdue loans, Due Date Range or Loan No. and Click the

At the Home Screen you want to Select the Cash Till Transfer, like the photo below, Click the Magnifind Glass And select the till you are want to transfer out,