You never really know how many pleats you'll have until you actually lay out the kilt and figure where the apron center stripe will be and where the sett falls relative to the apron edges. It might wind up being more or less than 20 pleats, depending upon how much you have allowed.

Be sure that you test pleat your tartan using the size pleats that you'll actually have at the hips, and do it with the tartan and pins, rather than by scanning and looking at it on the computer. If you choose to use wide pleats, your kilt will look different that the kilts that you show in your post. The only way to tell for your tartan is to actually pin it up. Sometimes what you think you want to do doesn't work at all.

And once you've roughly pinned a half dozen pleats (like what's below), stand back about 20 feet and see what it looks like.