Sounds like it's a reference to starting loads for BP handguns maybe? Hard to believe they suggest powder equivalencies to bullet grains of ML rifles 45-cal and above.
Also, what's the sense in starting with 50-60 grains anyways, if you plan on shooting beyond 50 yards.
Every hunter I've been in the woods with wants a load that harvests 100 yards minimum.
Most inline hunters today double-that-amount. Most ML inline boards are discussing loads that reach as much as 400 yards nowadays.
My very first load with my last five purchased MLs was 80 grains. I recommend that as a starting point. Heck, I only increased another 5-10 grains from that 80 number, before settling on a permanent load, shooting 180 grain and 200 grain sabot/bullets, using Blackhorn 209 powder.
No, I have it right in what he said. He recommended a gr of powder for every gr of bullet weight for rifles.