If you see factoring concept it check the planned working time and divides with divisor(30) even you assume he joined on 16.01.2015 according to system planned working time is 16 days now when you use factoring concept you get output as 533.333 (1000/30*16) 16-31 = 16 days.
even we can bring out put like below as well 16 to 30 = 15 days 1000/30*15 =500
It differs when it comes to Prorata i.e let assue that your record dates are like below 16.01.2015 - 31.01.2015 now maintained as 1000 when it comes to prorata it gives output for 16 days (16 -31) i.e 1000/31*16 = 516.12
"When you are checking for prorata there is no concept of 30 days it is already designed in such way check planned working days and prorate accordingly.
Remember that we have to look for alternative if we wanted 30 days as divisor"
Factoring we can achieve 30 days calculation as well irrespective of planned working time.
If you understand above two different things you can either suggest customer or provide an alternative solution.
Mean while when you look at the PCR which are attched is consideration of splits as well for factoring when splits are there it leads to wrong calculation.
Regards
Venkatesh