Hi Anand,
You requirement would be opposite i think so. How could be possible if employee joins after 20 of the month then he will be getting more quota then who joined on 1st week of the month.
Confirm with the client once again.
How you are calculating above your requirement?
You can go through the below link by which can able to find out where and how you will insert it in the Schema.
Differentiate PL entitlement based on the joining date
Absence Quota Generation Monthwise Constant with Mid Month Joinees Pro Rata.
Regards,
Sankarsan