It means the longest possible run between two consecutive booked halts, commercial halt or technical halt, of Indian Railways. But the train may stop in between this section due to other reasons like signal failure, loco failure, track work etc. This will not taken in to account while considering the term non-stop run.
Longest non-stop run in Indian Railways Wikipedia
Here the table is created in the sequence of lengthiest and fastest non stop run.
It refers to the longest distance between two consecutive passenger halt (commercial halt) stations. There may be one or more technical halt in-between these two stations. Hence it should not be treated as a non stop run.Here the table is created in the sequence of lengthiest and fastest run.