Under Settings > Configuration > Default values there are still a few values that need configuring. Here you can indicate whether you want to give a discount or when payments are usually due. To begin with, only a few fields will need your attention: values for discounts, due dates for invoices and reminders, and the validity period for estimates. For now you can ignore the rest.
All of these values are later used as default settings and can be freely adjusted at will. So it will be very easy to enter a longer payment period for a specific invoice or to shorten the deadline for a reminder in a particular case. Default settings merely serve to simplify the process by ensuring that a variety of fields are filled in ahead of time.
Expert tip: Later you can custom-tailor the values for each individual customer to accommodate deviations.