Plus, don't forget that it is possible to buy 1 seat and see 3 disappear from the fare buckets (1 from each J, D & Z), as there is overlap between the buckets.
Essentially it will work something like this (and to make it easier to understand I am not allowing for any oversell)
Of 14 suites all 14 can be considered J. Of the same 14, say 10 Can be considered D and 7 can be considered Z. So when the flight is released you would have J14, D10, Z7 Because the data released by VS to site like Expert Flyer stops at a Max of 7 you actually see, J7, D7, Z7.
Now as seats are sold the following pattern emerges
J14, D10, Z7 (starting buckets)
J13, D9, Z6 (A Z class sold) shown on EF as J7, D7, Z6
J12, D8, Z5 (another z class sold) shown on EF as J7, D7, Z5
J11, D7, Z4 (another z class sold) shown on EF as J7, D7, Z4
J10, D6, Z4 (A D class sold) shown on EF as J7, D6, Z4
J9, D6, Z4 (A J class sold) on EF as J7, D6, Z4
J8, D6, Z4 (another J class sold) on EF shown as J8, D6, Z4
J7, D6, Z4 (another J class sold) on EF shown as J7, D6, Z4
J6, D6, Z4 (another J class sold) on EF shown as J7, D6, Z4
J5, D5, Z4 (another J class sold) on EF shown as J5, D5, Z4
J4, D4, Z3 (another Z class sold) on EF shown as J4, D4, Z3
And so on.
This is a little simplistic (and there may be some parts of it that aren't correct), but it helps illustrate what happens.
Paul