Mike's post aptly demonstrates the 24pt-23pt directive (see #49-51, #66 and #75 in the tutorial), which did not exist in the previous tutorial. That is, for purposes of the hit-more-6 rule (explained in section 10), the 24pt and 23pt do not count as owned points. (For purposes of underlying definitions, such as to qualify @ or P, or to disqualify W or Q, the 24pt or 23pt is an owned point.)
In the position at hand, the 24pt-23pt directive reverses the previous identities of $ and %. Only anchors more advanced than the 23pt have meaningful value in the early game; hence the change. Now, $ (Slot) translates to the stronger play of bar/23 6/5, and % (alt slot) is the weaker (incidental 24pt-making) play of bar/24 6/4. [Another example is that for 31P-11, you ignore ownership of the 23pt and use capital E for 24/22 6/5(2) rather than for the weak 24/23(2) 6/5(2).]
W (Wild; i.e., split and slot) is a slot-related family. According to the slotting priority (detailed above diagram #72 in the tutorial), the "which point" ranking is 5pt, 4pt, 7pt. As Mike noticed, the letter W is defined such that the back checker moved ends up as a blot. That is, W never anchors, even on the 24pt or 23pt. (In other words, bar/24 6/4 is not in the W family unless the resulting 24pt checker is a blot.) In this position, bar/23 8/7 is promoted to the second member of the W family (w), while it is the third member of the $ family (italic $).
Style letters are fun and aesthetic, but may occasionally trip you up until you've practiced them. Areal letters are simpler to use: The 5pt is closer (to the 6pt) than the 4pt; thus E = Bar/23 6/5, and e = Bar/24 6/4. Also, numerals typically work well for enter-and-slot plays; here, 5 = bar/23 6/5, 4 = bar/24 6/4, and 7 = bar/23 8/7.
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| XGID=-b----E-CA--dD---c-e-a--AA:0:0:1:21:0:0:1:0:10 | |||||
43Z-63H-21 | |||||
Bar/24 13/11 is similar to 21S (21-split-and-down) in the opening position. [The "split" element of a Nactation play refers to simply moving a back checker, regardless of whether it anchors or creates blot(s) or advances an existing blot.]
The letter Z is "reverse split," meaning to split with the small number and come down with the large number. Bar/24 13/11 fits that definition. However, people learning Nactation (and opening plays are the place to start) find it easier to remember S, the first letter of Split, which is the reason for the convenience clause (introduced in #5 and defined above #62 in the tutorial). By this clause, the option of 21S (for 24/23 13/11 or bar/24 13/11, etc.) is fine; indeed, it is standard.
If one of the numbers is blocked by a point that does not exist in the opening position, I tend to use Z these days. (This should make Tim happy.) For example, 31P-43Z can be 31P-43S by convenience clause (and some people may well prefer it), but I'll use the former because it matches the traditional notation of 43Z in the opening position. [The same applies to 42P-32Z, though it matters less as opening 32Z is rarely played.]
The reason the convenience clause works so nicely for opening 21S, 41S and 51S is that you cannot bring the ace down: it is blocked by the opponent's midpoint. Likewise, for a play that enters from the bar with an ace and comes down, you can comfortably use S instead of Z. In fact, you can even use D, and the larger the non-ace number is the more likely I am to do just that. For bar/24 13/7, 61D seems at least as easy to understand as 61Z or 61S.
There are extra ways to nactate candidate plays when (as in this position) half of the play enters from the bar. For Nactation characters, you are allowed to either include or waive the entering portion. For bar/24 13/11, S or Z nactates both move portions, while D nactates just the non-entering portion. For bar/23 6/5, E or W nactates both move portions, while $ or 5 nactates just the non-entering portion.
Nack
[Mike: It does not affect any of the Nactations, but your post shows a position of 43Z-52H-21, whereas the thread is for 43Z-63H-21. Unless you are certain that was just due to a mis-posted diagram, might want to check your rollout files to make sure there that the 8pt-6pt distribution is three-five in the files named 43Z-63H-21, and that it is four-four in the files named 43Z-52H-21.]