Why does my client have to pay the entire balance now if I have a deposit and remainder due 7 days before the event?

Let's say it's April 10th and your client is viewing a project starting April 15th with a 50% deposit, remainder due 7 days prior.
Your client will need to pay the entire amount of the project because they are now less than 7 days before the event.

If your client is viewing the contract on April 10th and your client is viewing a project starting April 30th with a 50% deposit, remainder due 7 days prior, then they'll be able to pay the 50% deposit now, and the remainder due on the 23rd.