@Kate391 - when you block, you need to think of it as blocking "nights" not
days. So using the calendar from your listing. What you see here is the options for check in dates for the guest. That means the first NIGHT they can stay with you. In this case, January 19 is the first night and they can check in during the day of Jan 19.
They can stay through the NIGHT of Jan 26 and check out on Jan. 27 (which is blocked or booked on your calendar) See on the check out calendar, the date of the 27th is available - so checking out on the 27th is okay but staying overnight is not available.
So when you block a date you are blocking that night's availability. If you want people to be able to stay over on that night, you would only block up until the day before.