It means the order that the competitors are in when looking at the 'Competitors' Screen.
So, if you were about to time the first run and you have the competitors sorted by start number, or had just created a start list, it would make life easy because they would be sorted in the correct order and come up as expected in the start area of the timing screen.
If you had it sorted randomly you would need to enter each bib before they start since the system wouldn't be 'guessing' who is next. This isn't the end of the world, but it's always easier if you don't have to key them all in as you go.