So sorry for the delay. I’m assuming it’s gathered by a basting stitch and then stitched into place. These are a little tricky and, honestly, I think it’s more of experimenting with your pattern. Generally, when something is gathered it’s usually 1 1/2 times the finished length, although this may vary according to style. So you can create the pattern based on its current size but then extend the neckline to make it longer, maybe by cutting and splitting the center of the neckline and spreading it apart. I hope this makes sense.