@Brandon88 You have a big problem...................when you have folks checking in on the same day and give a late check OUT ---- PROBLEM...
I don't know why or how Airbnb gave them 3-5 window..............most of us check our guests in after 3pm. And 5 is kinda late!
Most of us verify with the guests inadvance on check in time. And I personally NEVER give late check out unless I am 100% sure no guests are coming. IB instant Booking seems not to be your friend on this one.
I don't use it but most/many hosts do.
Somehow you might wanna work with your guests checking out and contact the guests confirming their check in time....some will say 3, 4 and show up at 8pm............wish I had the answer for you...... you can also put a time between guests - or no last minte bookings.
good luck and happy hosting, Clara