How do the number of points indicate the size of the blanket they appear on?
There appears to have never been an original standard to point markings. But during the 19th century Hudson’s Bay Company did establish standard sizes that they would accept from their suppliers and as a result most British mills adopted them. American mills generally made their blankets slightly smaller and lighter than equivalently marked English-made point blankets.
While a larger point blanket will naturally weigh more than a smaller one, the actual weight per square yard of blanket cloth would be the same for each blanket size as long as they are from the same mill and of the same grade. From time to time various grades of blankets were available and blankets of the same dimensions and thus the same number of points were produced in both heavy and light grades. For instance during World War I HBC marketed lighter weight point blankets in grey and brown colours along with their standard line of colours in the traditional weight cloth.