Below is an example route book:
1st column: total/cumulative/overall mileage
2nd column: incremental mileage i.e. mileage since last instruction on previous line
3rd column: tulip diagram (see description below ***)
4th column: written instruction of what to do / additional info for this instruction
5th column: decrementing overall mileage i.e. how many miles left on the stage or transit, useful if you have a problem on stage, e.g. puncture or overheating, in order to determine best course of action
*** to interpret the tulip diagrams, the funny directional drawings in the third column, the dot at the bottom of the block signifies where you are / where you are coming from, and the arrow head signifies the intended direction of travel, so e.g. 1st one signifies straight on passing a side road on the right hand side, 2nd one signifies left at 4-way intersection, 3rd one signifies right at fork in road (often written as 'R @ Y' in the written instruction column) etc.
Some useful tips from Christian Edstrom, Travis Pastrana's co-driver: