my math sucks and I was only counting one side of each strand loop
I like to think in terms of top and bottom on my jig. The starting and ending hooks are at the top and the dowels are at the bottom Each time I send the spool of thread or mono down, that's an increment of one. I don't count the return.
If you think about it, every section is going to be increments of a half loops. If you count (7) when your thread hits the lower dowel you will end up with a 7 strands on one side and 6 on the other side of the dowel of your first section. I usually count the bottom of the loop (dowel or hook). So you your top section is 13 strands, the next is 9 (5 wraps) and bottom ends up with 3 strands. Once you fold in have and "unwind" you have a staggered 26/18/6 leader. It would seem like a jump down from 18 to 6 is massive, but because the leader is staggered, it's more like 26/22/18/15/9/6 (I think I counted that right). It's pretty smooth and you won't even notice the taper unless you go looking for it.
As for casting? Like butter. Even for a hack like myself who has fundamental issues to work out. It's more difficult to get wind knots with the furled leader, but I have managed it a few times. The leader will not make you a better caster, but they do roll out a lot smoother than a standard tapered leader. The biggest plus, is they have zero memory. Roll it off your reel or off a spool and it lays limp and straight. No tendency to curl. No stretching and straightening to do. Put on tippet, fly and go.
How you spin it is up to you. Some instructions say to clamp the bottom and spin each side until you lose 6 inches of length. I grab a second set of hands (you will need two bodies to do it with out screwing it up) remove the termination side, unfold it so I've got one long bundle of strands, hang a 19mm socket near the middle. Hook up the drill, let the socket sag about a foot and let'er rip. once the socket has come up a foot (or so) I stand the whole thing up, keep tension on the whole thing (with out letting the socket spin) and fold. Once folded, release the socket and allow it to furl.
If you let up on the tension at all and allow the leader to go slack before it has been furled you will end up with "bubbles" in your leader. It's not trashed, it's just not aesthetically pleasing.