Interesting, I've never seen momentum referred to in pound/seconds. I wonder why they do that seeing that momentum = mass x velocity and the pound isn't a unit of mass and seconds aren't units of velocity. Slug ft/sec or kilogram meters/sec if you like the metric system are typically what you see in physics/mechanics. Technically what they use is incorrect. I didn't check your values but they appeared to be values that made sense as slug ft/sec. Anyway it isn't a big deal I just have never seen it.