My understanding is that a paid appeal
is a new application because you are submitting new documentary evidence. However, I also understand that a re-application/paid appeal retains the same reference number as the initial application.
It makes sense to me to approach your re-try of HSMP as a new application because you are now going to be presenting earnings information, which must go back 12 months -- that is, the 12 months prior to
today (or the current date), yes? (That is, not 12 months prior to the date of the original application.)
Plus, if you are only now able to show 2 years of living as a married couple, it again makes sense to me that the new application would be dated at the current date rather than from April.
I suggest that you do a "search" (see the options located below the "immigrationboards.com" banner above) and ask the computer to look for all posts with the words "paid appeal" in them.
Hope this helps! Good luck!