A little bit of info from Alan over in Evreux :

Apparently to try to keep an accurate record of distances, the race organisers stop every treadmill every 4hrs and take a record of the distance(s).

These are then put in manually to a spreadsheet – which is then viewable at the race.

The treadmills themselves are then reset and the distance(s) restarted from zero.

The race organisers are also periodically checking the treadmill distance readings hourly, when they can.

All the data is being kept on a central server and will be able to be checked fully at the finish, which Alan (who is a registered official course measurer for the IAFF) thinks may well be necessary to avoid any possible recording errors.

Hopefully all the distances listed so far will be accurate, but naturally any and all total distances will need to be confirmed at the end of the race.