That direction is oddly written. Usually, it will say something like "work as per back until armholes" or "work as per back till work measures X."
But, I don't think you need to overthink it too much. Go to the back, which you already worked and count 32 rows back/down from the shoulder. Place a small marker here (different colored yarn) and work the front till you are at the same level/length. Then proceed with the front directions as written.