Help with Vintage Beehive cardigan

My first time posting, I am terribly stuck in this pattern. No clue what it means, if anyone could help me so that I can finish my sweater for my daughter, I’d appreciate it greatly!

Buttoned cardigan- back part - cast on 65

  1. Ribbing rows-done.
  2. Change to bigger needles, continue in stocking stitch pattern until work measures 8” ending in Purl row- done.

(Next row before shaping armholes, that I have no clue what they mean for me to do)

  1. “ At this time divide work on two needles to obtain width. When knitted to correct tension, this width should be one half of the finished chest measurement, whilst retaining the desired length.”

??

Hi and welcome!
Yup, that’s a stumper all right. I’d skip that cryptic vintage direction and move on to shape the armholes. It all seems straightforward from there.

I know, right?! I’m afraid to move on because I added in my own Celtic knot cables and I won’t know where to go back to to fix. I also have another pattern just like this in a mans size that I was so happy about and has this same (absolute nonsense) direction, in the same spot. I want to know what it means and never came across such a thing before, in s pattern

.

The rest of the armhole shaping reads as usual but you could add in a lifeline if you’re concerned. The other thing to do is look at the directions for the fronts and see if there is anything unusual there especially in the area before the armhole shaping.

The only idea I had was that it had something to do with compensating for short needles? Doesn’t completely make sense but I’m just as puzzled as you are. Vintage patterns are a whole other country.
I have a brief translation from a magazine for some vintage abbreviations but apt.

Thank you for taking the time to help me. I’ll try your suggestions!