Hi, Pilot Pete. You are probably looking at a MOTNE report, which is different from a SNOWTAM.
A MOTNE report is an 8-figure group appended to the METAR, where figure:
1 and 2 =Runway Designator
3 = Type of deposit
4 = Extent of Coverage
5 and 6 = Depth of deposit
7 and 8 = Braking Conditions.
The MOTNE report is derived from the same observation/measurement as the SNOWTAM.
Nick.