To set the default number of nights displayed when making a reservation, follow these steps:
Property Settings > General > Property > Preferences
Within the property preferences, scroll down until you find the "Booking Forecast Settings" section.
Within this section, you will find the "Average length of stay" field.
Here you should enter the number of nights you want to appear when searching for availability for a new reservation.
Once the number of nights is entered in this field, it will be set as the default configuration for the stay duration when making a reservation.
In this way, each time you search for availability, the configured number of nights will automatically be displayed.