hi hugh
it does stand for commertial the 6 and 8 ply steel braided rated tyres with a "C" have a higher psi per tyre size than the textile type radial because the side walls are stiffer and thicker.
take your max van weight divide by 2 single axel or by 4 twin this gives the load factor per tyre look down the chart for tyre size then across for the load factor the correct pressure will read across the top.
mine is 1070kg divide by 2 = 535kg on 175x13c 6ply > gives a psi of 42
assuming your van is a bit heavier on 8 plys the psi is 42 also or the next box along that is 45 psi
hope this helps
colin