Answer to this question is simple … ’Cause I have studied there ( Himachal campus).
As it depends upon day scholars and hostellers strength.
Sections are provided to the student at the time of orientation.
Firstly sections are made for day scholars and it can contain some hostellers depending on the strength of day scholars/hostellers.
And then hostellers sections are made.
Sections for both above are made on alphabetical order i.e., Names starting with A will came first than B and so on ……