Hello @Ana417,
It's not possible to set up a limit for check out days unless you limit all stays to exactly 1 week, no more and no less. You can do that by having a minimum and maximum stay of 7 nights and check in on, for example, Saturdays only.
Setting the checkout day is something that a lot of hosts have asked about here but Airbnb hasn't provided the facility.
You could search in the "Host voice" section of this site to see if someone has suggested it.
If you find one then give it a thumbs up. If not, make a new request.
Airbnb promises to consider suggestions made there if enough people give them a thumbs up.
They don't say how many thumbs up though.
Click on "Discuss" at the top of these pages and select "Host Voice" from the menu.
Steve.