Hello, the instructions on the attachment do look weird.
I remember finding a good Youtube video on Butterfly Stitch (Purl Side)
a while back (7.25 onwards for the Butterfly).
KnitPurlHunter has also done a video showing how to do Butterfly Stitich (Knit Side)
(3.30 onwards for the butterfly).
For some reason Youtube videos are muted on my computer and I don't know if it's them or me. If it's Youtube, it should be possible to work out, from the videos, what to do with the centre stitch of each butterfly.
Hope that helps.