Hi @Jadelyn1
If your check-in time is 4pm
Same day notice 2pm means a guest can book today from 12:00AM all the way up until 2pm today and still check-in at 4pm.
Some Hosts don't have an issue with this (doing same day turns), if the property can be cleaned in several hours. That said, some Hosts still give themselves a bit more time and say the guest can book today and check-in today, but only up until 12noon. This would still allow 4hours to clean in case of a late check-out or the listing requires more cleaning time than normal.