A belated welcome to the forum, @DET !
In your post you mention applicants and invitations. They’re two different things. If these people submitted applications to your listing, you would have responded, set up a phone or video chat with the one you were most interested in and if you and the sitter felt it was a match, you would have confirmed the sitter. The sitter would have then accepted and it would be officially on the books.
You also have the option of seeking sitters out and sending them personal invitations. It’s important to send a personal note with an invitation if you hope to get a reply. You may find a sitter that way but it’s a long shot. The same confirmation process takes place, you confirm them, they accept.
Until a sitter accepts there is no commitment.
As has been said here many sitters don’t bother to update their calendar as it’s not very user-friendly. What it is good for is to see when a sitter is already booked for a THS sit. These dates have slashes through them.
A good listing is the best way to find a good sitter. I would suggest you add your listing to your forum profile. Forum members will then be able to give you helpful suggestions to make your listing as effective as possible! Here are the instructions: How to add your listing or profile to your forum profile
It’s also a good idea to read the forum. Use the spyglass icon on the upper right to enter questions or keywords. Many subjects have been discussed.
Good luck. You came to the right place for assistance