You haven't seen a weird file format until you've dealt with one of other embroidery formats, .dst. It's literally converted from an old paper tape format so it's like 21 bits per row, each bit indicates part of the length of the stitch so a 1 in place 0 means 1mm, place 1 means 3mm, then 9mm, -1, etc. The original format was holes in the tape and they just kept that idea for the past decades. You add all the 1s to see how long the stitch is. I had to write a converter in Go as my first Go project to integrate into a larger project and it was a trip.