A lot of that is "duplicate" volume being registered on both the venture and OTC. A look at some of the larger blocks that went through on PTK.V and POETF shows the exact same number of shares at the same time being traded on both venues. So it's not necessarily the case that the US volume is in addition to the Canadian volume.

This is probably a function of how US trading houses can send trades to the Canadian side automatically where there is more liquidity, but the volume registers in both places.