Thanks, Nat!

It's a single stack weight system and I'm not really sure how accurate those numbers are. It would be interesting to test it with free weights to see if I can lift the same amounts. I'm going by the chart in the manual for how many pounds of resistance you get with a certain number of stacks. I know that my 20 lb. dumb bell set was getting way too light for me, though, and will probably be getting a 40 lb. set in the next week that can have additional weights added to it later.
If I remember correctly, a bale of hay weighs in the range of 60-70 pounds and the bags of grain were about the same.
DH was pushing for a barbell set with a weight bench, but I find barbells akward to work with.