Hello Purvi, 

It refers to NEET MDS roll number. 

During registration, one needs to select the stream (medical/dental), NEET MDS roll number, application number, name of candidate, date of birth, security pin, etc. After this step, they are required to fill their personal details such as father and mother name, address, category and other details. Candidates must be mindful of these details, as the details once filled cannot be edited and the similar information filled here will be required at the time of document verification and admission.

I hope its clear to you.