I'm sure you found the answer to this by now, but just in case you haven't:

My husband gives 10 days for his customer to pay invoices.  This is changed by going into your customers, and going to the payment settings.  I found it also works on the statements, as well as invoices.  However, I do invoicing on the last business day of the month, so they are all run on the same day.  When I run a Past Due Statement, I go to the customer and change the payment setting to "Due Upon Receipt."  Once the Late Statement is done, I change it back to the 10-Day grace period.

Hope this helps.  I also find QB difficult to customize, and sit and play till I find my way to what I need.