When you set up your profile, you are asked to select a cancellation policy. The option you select dictates how a client will be charged (or not charged) when they cancel. Here is a description of the policies:
Rover Sitter Cancellation Policies
Flexible
A full refund is available if you
cancel before the dropping your dog is
the care of the sitter. If cancelled
on or after the beginning of the the
stay, a 50% refund is available for
the first remaining seven days of the
stay, and a 100% refund is available
for any additional days.
Moderate
A full refund is available if you
cancel by 12:00 pm the day before the
stay begins. 12:00 pm is determined by
the sitter's time zone. If cancelled
later than 12:00pm the day before the
stay begins, a 50%refund is available
for the first remaining seven days of
the stay, and a 100% refund is
available for any additional days.
Strict
A full refund is available if you
cancel by 12:00 pm one week before the
stay begins. 12:00pm is determined by
the sitter's time zone. If cancelled
later than 12:00 pm one week before
the stay begins, a 50% refund is
available for the first remaining
seven days of the stay and a 100%
refund is available for any additional
days.
Example:
If cancelling a 2 day stay after the
deadline, you will be refunded 50%.
If cancelling a 14 day stay after the
deadline, you will be charged 50% for
the first remaining 7 days and the
rest of the unused days are refunded
in full.
If you have questions, please contact
Rover Support or call [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team]
From your description, your cancellation policy is currently set to either flexible or moderate. You can change your setting at any time in your overnight boarding profile. Changing your policy to strict would prevent you from losing all of that income for last minute cancellations.