It is different depending on what part of the country or world you are buying it in. The term "bag", isn't even used in a lot of places. That is mainly an east coast US, specifically NY/Phili,etc, term because over here it is sold in individual wax paper bags with a stamp. However for example on the west coast.. that is not how it's done. You go out there and ask for a "bag" or a "bundle" and people will look at you like you have two heads. Even in other parts of the east coast like New England and down south, it's sold differently without the stamp bags..
So there is no general explanation for you.. you have to figure it out for whatever area you are in. The different slang, the packaging, etc. Usually on the east coast, single wax paper bags of H can be anywhere from .03 on the small side, like in NJ, to .1. Bundle is 10 bags in NY and CT for example, but is 12 or 13 in other places on the east coast. See what I mean? It's all different depending on where you are.