In GUJCET and other pen-paper exams the question numbers are shuffled in each paper. For example, the question paper you will get, the first question of yours can be the 11th question of the student beside you. These are the measures taken in order to control cheatings in examination.

Now as per your question, it is said that each of this shuffled question paper will have a code corresponding to it. So you have to fill that question booklet code on the OMR same to same as it is printed on the Question booklet. In GUJCET they create 20 kind of papers containing same question but the question papers are shuffled.

To know more about GUJCET visit the link provided below:

https://engineering.careers360.com/articles/gujcet

I hope this answer helps. All the very best for your future endeavors!