Number of attempts for ipcc

can anyone tell me the logic behind this formula in contract costing:

1/3 *notional profit*cash received/value of work certified

can anyone tell me the reason for recognising profit on proportionate basis in Contract costing

How many ipcc attempts are available on 1st time  registration ?

my 4 attempts are completed on 5th time there is any limitations ?

How many attempts are applicable on ipcc ?

My 4 attempts are completed there is any limitaion on 5th time ?