Multi Unit Residential Building - Phased Occupancy

I understand that in order to obtain this credit, 10% of the first 100 dwelling units and 5% of any additional units of the multi-unit residential building must be tested for the specified LEED parameters. For our project this equates to 11 rooms. Our client intends to allow tenants to move into pre-rented units that have been completed (approximately 15 units) prior to construction being complete for the entire building. My question is this: In order to meet the requirements of this credit, must all the IAQ testing be completed prior to any residents moving in? Or can we take samples for a portion of the pre-rented rooms (i.e., just 3 units at first), and when construction is complete for the remaining units, then complete the IAQ testing to fulfill the requirements (the additional 8 units)? This will mean some residents have moved into the building before all testing is complete. I'm unsure of the implications as I suspect phased occupancy in a multi-unit residential building is fairly common? Any advice that can be shared would be much appreciated.