I guess by internal quota you mean the 85% state domicile. It is issued by the government as a proof of your residency. Let me explain the procedure

Usually you have to qualify at least one of the following criteria in order to obtain the domicile certificate in any state

1. It is issued to only permanent residents of a state/UT for at least 6 years (this time may vary). It is 3 years for delhi
2. If you are under 18, your father must be a verified domicile holder
3. You must own property in delhi
4. Your name must be registered in the voters list

If all these conditions hold true, you can apply for a domicile certificate.