Vintage crochet patterns

I love vintage crochet. Some of the most beautiful things come from long ago. However, the way some of the patterns were written is....well...confusing to say the least.

Take this chair set. Note that the foundation chain instructions say to crochet a chain 22" long with 15 chs to one inch. Then it goes on to tell you that you need 29 shells on this starting ch and to cut the excess. That seems pretty wasteful to me. Why would I want to chain any more than I need to? What I did was to figure out how many chains I would  need to get 29 shells and chained that. It turned out to be 286. Not sure what the pattern multiplier is, but I couldn't see any reason to waste thread or yarn by chaining more than I needed.

Edit: After thinking about it, the multiplier is 10 + 6. You would count for 28 shells, then add six for the last one. IOW, count for one less than the total # of shells, then add six more chs.

By the way, I'm using WW yarn and a size H hook and am making the chair back as a wrap. I hope it turns out like I'm seeing it in my head. Perhaps it might turn into a cape with it's shape, we'll see.