Documents required for H1b visa with diploma(3years)+engineering(3years) education

My case was received for H1-b-2017.Recently, my case status is change to RFE. They are asking for document, which is mentioned by the university that, “I got admitted to the 2nd year degree course because, I had completed 3 years of the diploma course.”. It is very hard to collect this document . Is this document needed… help me…

My education details: I have completed diploma in computer science and after that i have joined direct on 2nd year of B.Tech course on the same subject computer science.

My work experience: 7.5 years