I did a bit of research on "setting" eggs. It is apparently an unnecessary activity for fresh eggs straight from the nest. However, when eggs are transported in shipping they often get shaken quite a bit, which can result in a detached air sack. Setting allows the air sack to reposition if necessary prior to incubation. If the air sack sets in the wrong position it could result in a suffocated fully developed bird. Additionally, the eggs may not be at an ideal temperature. I drastic seeing in temp could result in shock to the egg or even condensation in the air sack which could also be detrimental. So the practice of setting the eggs at room temp (60-70 F) for 12-24 hours is used to give Spotted eggs a chance to acclinate and settle properly prior to incubation.
Since people will also delay the activity of rotating the eggs for a few days (I read cases of up to 7 days) to allow detached air sacks to reattach in proper location. You put the eggs in the rotator or tray but hold of on rotating. This why they are position properly with narrow end down causing the air sack to sit at the fat end in a steady position to reattach and for gravity to set the yolk properly below the air sack nice and center. I will give a few days. 7 days scares me. I am thinking 12-24 goes at room temp depending on the time of day they arrive and then 3 or 4 days in the rotator with no rotation and then I will plug in the rotator.