Awesome number crunching. That being said invited to apply is not the same as people who actually got the PR.Hi these links might help you.
There were a total of 203213 interests submitted on 2020, out of which 13400 were invited to apply (Ref: https://www.canadavisa.com/canada-immigration-discussion-board/threads/pgp-2020.646383/page-176#post-9121347), i.e., remaining in the pool = 203213-13400 = 189813
In 2021, 34500 were invited to apply (Ref: https://www.canadavisa.com/canada-immigration-discussion-board/threads/parents-and-grandparents-sponsorship-2021.744749/page-86#post-9737915), i.e., remaining in the pool = 189813 - 34500 = 155313
In 2022, IRCC announced that they will be "sending invitations to apply to 23,100 interested potential sponsors" (Ref: https://www.canada.ca/en/immigration-refugees-citizenship/news/2022/10/reuniting-families-across-the-country.html), i.e., minimum remaining in the pool = 155313 - 23100 = 132213
This year, in 2023, "RCC will be.. sending invitations to apply to 24,200 interested potential sponsors" (Ref: https://www.canada.ca/en/immigration-refugees-citizenship/news/notices/parents-grandparents-program-re-opens-fall.html)
Hope these numbers are what you are looking for. Best of luck to those who are waiting.
Q: for those who are invited to apply but did not get the PR are they still in the applicant pool?
Also how is the determination made of the first 15K out of the 24K that will be invited to apply this year? Is there a serial number that is given out and a wait list for those from 15-24K?