That link says "A grade 3 paper has a printing range of approximately three f-stops". Is there some standard that says this, or a chart of approximately the printing range of various grades of paper? I guess I could test it myself by doing a test strip... I'm currently using Kentmere VC select Lustre.
On the second page, see the table "ISO Range". To covert it to stops, divide the ISO Range values by 30, i.e. Filter 3 equals ISO Range 90, 90/30=3 stops.