That is probably a little low for all 12 classes they're running. The last race at Meridian had about 115 riders.
I would expect more like 80-100 riders, maybe more. With the split race format the course shouldn't be too crowded even though it is short.
There was over 100 riders at this hare scramble at Oak Grove above Baker FL. The trail distance was a little over 5 miles and took about 20 minutes a lap for the AA riders. Toward the end the muddy spots were getting bad but it seemed most people still had a great time..