Oops, didn't notice the typo-o in those daily distances when I copied and pasted from the source. Clearly its not 2.5 miles but 25 miles.
In summary, Franks's strategy was:
Wake at 3am, run 25 miles at 10-12 minute pace
Run another 25 miles
Then, cover as much ground as he could with remaining strength by dark and turning in for the night
Rinse and repeat