Why is my booking form saying date unavailable?

I made a booking form and set the dates for on specific day that is available for booking. I went to test it out and every time on that date I put in says that date is unavailable?! 

I have made a test but I was not able to replicate the problem. Is it possible that you have made deletions from your form's submissions? Also, can we make an actual test on your form to see if the problem persists specifically on the form?

Thanks.