Not my board TC. I could be wrong but my recollection is of a number less than 200 on one of the occasions that I have looked at this. There may have been two SK figures.
I would expect these to be just initial guidelines based on a standard risk profile. It's also possible that they are claimed or contracted minima from each providers' management. The ARCC's Rescue Co-ordination System (RCS) will do the maths to produce an initial estimate for a particular job, based on the prevailing met and so on.