Your booking panel may show one rate plan for some stay lengths and two for others.
Why this happens. The booking panel lists every rate plan Guesty returns for the dates searched. No site setting removes plans. Which plans appear depends on the rules configured on each rate plan in Guesty, specifically minimum and maximum nights, booking window, and other conditions.
What you can do. To make a plan appear for a given stay length, adjust that rate plan’s rules in Guesty. The site caches each quote for a few minutes, so after making changes, wait briefly or change the dates before you test again.