I've used a heart rate monitor while skating, and those numbers in the calculator seem about right. Maybe even a little on the low side for me. I wore the monitor a lot in the beginning, but not as much now that I know the range.
For doing low freestyle (scratch/sit spins, single jumps up to loop, program run throughs) a 60-minute session for me burns about 500-550 calories. If I'm having a slow day with only MITF (pre-bronze and bronze test moves) and a lot of skating around aimlessly, it's more like 350 calories an hour.
For me "light" means moves, stroking, and general skating around, "moderate" is a typical freestyle session, and "vigorous" isn't a level I can maintain for a whole hour (program run throughs feel pretty vigorous though).