PCGS Pop meanings

In the Registry Sets, there is a pair of columns "PCGS # Pop" and "PCGS # Pop Higher". There is also a pair of columns labeled just "Pop" and "Pop Higher".
What do these labels mean? What's the difference between the "#Pop" and plain old "Pop"?
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Good question that I've asked before and I didn't like the answer. PCGS # pop and Pop are typically the same unless you are talking about a date with a lot of varieties. Example - a bust half date will typically have a higher pop # because of all the different Overton varieties for each date but are under different PCGS #s. In regard to the other 2, PCGS # pop higher and Pop higher - these #s take into account the higher pops for that specific PCGS # (1st one) and the higher pops for that coin including the different designations (2nd one). Here's an example and why I don't like it: I have a top pop 67 Red/Brown Lincoln that is a PCGS # Pop and PCGS # Pop Higher 1/0, but I do not get bonus points in the registry because the Pop and Pop Higher take into account all Red coins (deemed higher) for that date so now instead of a 1/0, it is a 1/63. It assumes that any Unc coin with a Red designation is superior, even if it's a 60. Confusing, but I hope that helps. If you play around on Coinfacts, you can see the pops. Click the related coins and varieties tab for that date and you will see what I'm talking about.
https://pcgs.com/setregistry/showcase/2819
The 1st two pop numbers shown in the Registry are the pops for that particular PCGS Coin Number. In the example below, "2011-S PR69DC First Strike".
The 2nd two pop numbers shown in the Registry, I think are supposed to be the total pops for ALL PCGS Coin Numbers that match that date/mint. In the example below, 2011-S Proof Saca for all permutations (reg PR, CA, DC). However when I looked at an example in my set, the total numbers were slightly off in those columns -- though they were pretty close (within about 1% to 2%).
Not sure if that 2nd set of numbers dont match exactly because PCGS doesn't update the registry pop info that often -- so the pop reports and the registries can get a bit out of sync? Or if those numbers are actually computed in a way that is different from what I thought?
For copper coins the first two pop numbers would be for the particular color class BN, RB, or RD of the coin in question ... and the second two pop numbers would be for all color classes combined for that date/mint.
Not sure how varieties are handled as I dont deal with those.
The image below compares the PCGS Slab Population Chart ... with a few lines from a sample Registry Set ...
My Coin Blog
My Toned Lincoln Registry Set
Can't resist:
https://youtu.be/gPoiv0sZ4s4
"Got a flaming heart, can't get my fill"
That was the best explanation. :-) The rest are still confusing.
http://www.shieldnickels.net
W> @WingedLiberty1957 said:
It appear the formula use for the last two columns is incorrect. The PCGS number 626897 is not included, but should be. This appear to be new PCGS coin number, and may not have been added to the POP formula when the number was added.
My 20th Century Gold Major Design Type Set ---started : 11/17/1997 ---- completed : 1/21/2004
Seems like something new management could simplify .... ? or add to the list.