One of the differences between knitting an item from a pattern or whilst creating one is the maths.  Mums jumper is now at shaping the neck stage which was punctuated by mutterings like 63 minus 9 divided by 9.  I assume the 9 is the number of stitches in the middle as she then said she hopes the neck won’t be too big.  I have every faith in her that it won’t be.