noun
furlong
FUR-lawng/ˈfɜːrlɔːŋ/
A unit of distance equal to one-eighth of a mile.
The first furlong spans one of eight equal stretches along the mile-long path.

Etymology
Originally a furlong was the length of a furrow in a common field. That agricultural measure became fixed at 40 rods, or one-eighth of an English mile.
In context
As they come back to the two furlong marker it is Ecstatic and Concorde Hero.