This refers to the total amount of air that is delivered to your room. This should be provided to you by your building services engineer/building management office. To specify again, this is the total volume of air delivered, which is a mix of outdoor air and some of the room air being recirculated back into the room to save on cooling/heating energy.
Note that an air change of one per hour does not mean that 100% of the air is replaced in 1 h, due to mixing. After one hour, with a one air change per hour ventilation rate, what remains is about 36%, 14% after two hours, and so on.