Sorry. I'll rephrase. All the silver is listed in the weight regardless of purity provided there is a purity and a weight.
All silver is accounted for, even those listed as billon. For instance this coin N#10865 will add 4.6 g of silver (11.5g X 0.40).
But for coins where the purity isn't listed or the weight isn't listed obviously they don't count in the total silver weight.