Per T&Cs http://www.clubcarlson.com/offers/4119046
Elite early checkin says up to 2 hours prior to normal checkin time
Elite late checkout says up to 2 hours after normal checkout time.

Edited to add: Of course if a 6pm checkout is listed as amenity for a specific room (i.e business class room in certain locations), then that is guaranteed...unless it says "based on availability" of course.