Don P--I see.
Well, for 20 years I have always put 100 at a time of either small or large pistol primers in the original Lee Auto Prime and it all has worked fine.
I can't imagine the large primers being resticted to 20 and the smalls to 100.
Does not make a lot of sense to me. I don't doubt that is what the instruction sheet says---but it seems illogical to me.