Compensation for delay of project by builder.

Dear Sir, My son, an NRI applied for a 3 BR flat in a venture started in 2016 in Mangalagiri mandal. He was allotted the flat applied for by the developer and allotment letter was issued on 22nd feb, 2016, where-in the terms and conditions were detailed. As per t&cs 1. The due date of the project was 3 years from the date of allotment letter; 2. Penalty Interest for delayed payment by buyer is 18% & compensation by the builder for delay is @ ₹5/- per month for square foot of super-built up area; 3. Liability of the developer for compensation for delayed period is limited to 5% of sale consideration, 4. The penalty/compensation will be settled at the time of conveying/registering the scheduled property; and 5. The precess of registration of property will be commenced on receiving the occupancy certificate (OC) received from the authorities. Further I submit that 1. NOC from fire department was received and occupancy certificate is awaited; 2. the project was registered under AP RERA act and its registration no. Available on developer’s web site. Project was delayed by almost 12 months (required to be completed by 22.2.19), now the builder proposes for registration of the property with out receiving the OC and not transparent in regard to the compensation for delayed period. In the light of above please guide me for the rate of compensation my son is entitled for from the builder as per AP RERA act.