This feature is one of the main ones keeping OnceHub users from migrating over to GHL. OnceHub allows for calendar availability to populate based on x number of days with availability. Instructions on how it works are in the link below. They call it a timeframe rule using the "available slots method."

GHL doesn't have the, "display the next ___ days with availability" filter and only displays openings for the next ___ number of CALENDAR days ignoring if there is availability on those days or not. This causes a significant issue over the weekends and holidays where a user's calendar might not have openings, or times when lots of appointments are requested. This is an issue because availability runs out in those circumstances instead of automatically opening up an additional day or days. We can measure significant increases in our cost per sale when there are not enough open days due to this issue and that keeps us from using GHL like we'd like to.

See the section in this OnceHub article on timeframe rules to see how this works highlighting the ability to "only count days with available time slots"

https://help.oncehub.com/help/timeframe-rules#:~:text=Only%20count%20days%20with%20available%20time%20slots%3A%20This%20is%20based%20on%20your%20availability%20settings%2C%20minus%20blocked%20busy%20times%20and%20any%20previously%20scheduled%20meetings.