If a customer does not want to use all of their store credit or they do not have enough funds to cover the entire transaction you can use store credit and another payment method
Add a customer. Here is a link if you need more help.
Add Items to transaction
Click "Tender" at the bottom of the screen
Click the "Store Credit" Payment option
Enter the amount you want to charge to store credit.
Click "Add Payment" After this you will still be in the tender screen but the "Amount Due" will change.
Select your other payment method and enter the amount.
Click "Add Payment"
Click "Complete"