In the first “heat” the racing order is very straight forward.  The racers run in the order that they registered.  Every racer is assigned to a specific lane.  Notice that Bobby Thomas is assigned to lane #1.

NOTE: A “Heat” is defined as “when all racers have run down the track one time.

In the second “heat”, notice that Bobby Thomas has been moved to lane #2 this time.

NOTE: Therefore, in Heat #2 all the racers will run down the track again.

.... And in the third “heat” Bobby Thomas is now running in lane #3 ....

NOTE: ... and in Heat #3 all the racers run down the track a third time.

.... And in the fourth “heat” Bobby Thomas is now running in lane #4 ....

NOTE: ... and in Heat #4 all the racers run down the track a fourth, and last, time.