I think one is a metric designation and the last is a designation for the particular sewing machine style. In any case the idea is to accept heavier thread without snagging and also to handle the heavy fabric without breaking. Other identifiers are needle size 16-18, where size 11 is ideal for shirts. Mine says Size V-92, 40Z and F74. It can either be polyester or nylon.
Polyester has better uv resistance and nylon is a little better at moisture resistance.
I opted for poly, which is used for awnings in Seattle because the uv deterioration is more significant and I think nylon is more difficult to handle. I used a 1957 Singer of the type which uses mechanical cams for zig zag stitches. It's clearly a domestic machine but seemed to handle the canvas as well as a carpet machine. Actually you can pick from any number of suitable materials, and you may just happen to have something already. On the low cost side is a strong paint tarp, which has the density of jeans.