@Patrick2382 you need to switch on professional tools in your account settings. Then go to you listing calendar and add a rule set that only allows check ins and check outs on Saturday. Apply this to either high season dates or to the whole year. Come back if you need more help.
@Patrick2382 go into your hosting page. Then click on your picture top right. Then click on professional tools and switch them on.
Your current restriction on check in days is fine BUT it allows 8/9/10/11/12/13 night stays which then means the remaining nights are lost to you as your guests cat check in on anything except a Saturday.
With rulesets you can limit check in AND check out days. Plus you can only apply this to high season if that work for you.