Applicability of GST RCM on TDR - Goods and Services Tax - GST

Respected Seniors Experts I have a Querry Relating to GST RCM on TDR as below : Facts : My client is a Builder Developer. He has purchased a Land by entering into Conveyance Agreement. He has also purchased TDR for which will be used for construction of Additional floors. but nothing as such is mentioned in the TDR Agreement. Building is of Ground + First Floor (Commercial Units ) Upper 9 floors for Residential units. My question is : Whether GST RCM is liable for Construction of Commercial Area with respect to Purchase of TDR ? When calculating RCM in respect of unbooked Residential Units, I need to consider Whole constructed area or only upper floors ? Thank you in Advance