You will only receive a booking with a shorter length of stay than configured if the "short stay" feature is enabled in your Holidu account. If short stays are enabled, they apply to all of the seasons you have configured in your account.

This feature helps to increase the visibility of your listing as well as your minimum desired income, since you will always receive the minimum amount configured.

You can enable or disable it in your account.

Select the tab “Configuration”, and scroll down to “Pricing”.
Scroll all the way down to the discount section and enable or disable “Allow short stays”.