Why do you not want to answer this thread?(Your answer will be sent to Jeanette and Aytekin)
Wanna ask can the check-in date and check out date auto calculate how many day selected?
You can perform a calculation.
How to Perform Form Calculation Using a Widget
Here is my demo form: https://form.jotform.com/72961379302965
Feel free to test it and clone it.
Hope this meet what you are looking for.