22 box question

Hello everyone, I have a question. While reading the true account of the Mad Trapper of the Rat River, I was perusing the list of items he had on his person when he was killed by the Mounties. In the list of items, were 2 boxes of 22 rimfires, 30 rounds each. He also had a additional 4 loose rounds of 22 ammo. The time frame was 1932 and the region was the Artic Circle in the Northwest Territories. My question is, was it coincidence that he only had 30 rounds of ammo in each box that originally held 50 rounds. Or was there a brand of ammo of this era that held only 30 cartridges.

I’m been working on the Dunn Canadian .22 upgrade for the past week and I’ve seen no 30 round packs only 50’s. The boxes date back to 1890. See here http://22box-id.com/world/Canada.pdf. The earliest boxes that I have were Dominions. I’m not aware of any US boxes of 30 but perhaps there might be some Russian boxes. Early USSR boxes are almost unknown here because it was a closed country early on. I understand that it’s just in the last 50 years that we got a glimpse at their .22 ammo boxes.

It could also be typos in the list or just assumptions as to the contents of the boxes if they were sealed. Being the “Mad Trapper” maybe he tested 20 rounds out of every box:)