Here is link to course map for 12 Hours of Santos. Looks to be about 8.9 miles with 700+- feet of climbing per lap. For reference, Razorback had over 1,100 feet of climbing per lap and was about 10 miles.
Question is: How many miles and laps will winner do? With less climbing and not as much technical riding at Santos, I am guessing, winner will do around 140-160 miles which would be 16-18 laps.
Putt it in the big ring and forget about it!!