The article may be want to say about Piston Varnish Merit Rating
as I know, it is CRC procedure, but i forget the procedure number
It is used to evaluate the varnsih which usually appear (buildup) at the oil-ring area (as well as the piston are) after a certain period of time.
Rating scale is defined in the scale of 1 - 10
10: for ecxellent, no varnish
1 : heavy varnished
so, for varnish merit rating, higher is better