The same here,
I used it mostly in the last couple 24hrs endurance rallies. I know the total stage time with the average speed given by the organiser. Say that in our rally he gives 50km/hr average speed. I know that when the roadbook tulip hits 50.00 then I should be in the race for about an hour. More, it means I have to push, less it means I am ok. You can pace accordingly if you know what I mean.
In order to remember the times, people also stick a paper with total kilometers and stage times on the roadbook cover.
SS1-145-2:50 (Special stage 1, total 145 km, 2 hr and 50 minutes) . It is a personal preference I guess much like the roadbook marking...