When you come in for your Ordering Appointment, you will use that credit towards your purchase.
Let's say you have chosen $500 in wall art and have $100 in Print Credit, when you order, that $100 credit will be taken off your balance. So you will owe $400 instead of the full amount.
The reason we do it this way is if we included certain sizes automatically, you may not need or want the size given. The credit allows you to pick out what you want.