I can book a one-night stay for 6 to 7 July @Julie-and-Lincoln0
It seems your 4-night minimum starts from 7 July. How did you set it up, was it done through a rule set, or did you go and change the minimum stay on each of the dates on the calendar?
If you want the minimum stay to apply throughout the year, go to the Availability tab of the calendar and set up the global minimum stay there.
As there's so little availability left in July, you can perhaps reduce the minimum stay for those few nights, depending on whether you think you'll still get a 4-night booking there. Perhaps change the global minimum to 4, and then override the July nights to a lower minimum stay if the time comes closer and they're still not booked.