Head count means that there was probably an extra person on the plane compared to the check-ins.
I know that this can happen sometimes when people are re-booked by a gate agent and issued a boarding pass which will scan and allow boarding, but the person also has to be "checked in" which can be missed sometimes, or at least happened to my wife once.
Lap children that are in a seat also can cause this, but that's usually the first thing they check so it isn't likely to be the reason for an hour delay.
Can't help you with the turbulence though. The archive isn't showing up in Flight Aware for that flight number and day so no idea what the details were.
Home airport MDW, frequent visitor to MCO to see the mouse.
