I thought it might be a bit confusing. Here it goes:
When we say the first string, we mean the high "E". The second string, therefore, is "B", and so on. The last, or 6th, or bottom string is called the low "E". In referring to 12-string pairs, each set of parallel or octave strings is called a "course".
(I didn't know that until recently . . .)
So, on the "Guild 10-string guitar"
:
The first course, is "E", tuned standard, in unison - .010"
The second course, is "B", tuned standard, in unison - .014"
Third course, is "G", tuned standard, in unison - .022" (or .024")
The fourth course is "D", tuned standard, in unison - .032" (or .030")
(All of these so far make up a "Extra light gauge" set).
The fifth course is "A", tuned standard, and only one string - .043"
The sixth course is "E", tuned standard, and only one string - .053"
I had to actually loosen the truss rods in doing this, because there is less tension on the neck with this setup. You've added stress on the bottom, but take it away in another area. I like the sound of this a whole lot more than the jangly sound of the standard 12-string. Like I said, it sounds like a 6-string, but a whole lot fuller, like two guitars, or a guitar with a built-in chorus. AND it helps to slightly tune the unisons out of tune with each other. That gives it the richness.
The down side of this, is that it is expensive; there is no off-the-shelf string sets for this setup. I have to buy two sets of extra light gauge acoustic guitar strings, and toss aside the two As and Es, and then buy a single A (.043"), and a single E (.053" in order to make up a set for this beast!
So I save the tossaways, and buy the first 4 strings separately, to outfit my F-30R, which of course, is a 6-string.
All this trouble is worth it. Love the sound of my F-212. Can't put it down now . . .