It's a best guess calculation (statistics) based on some "known" info.
Here's something based on colors and models for Challenger
Example:
955 R/T convertibles built
Plum crazy was most popular color at 22.2%
So best guess is there were 955 x 22.2% = 222 Plum Crazy R/T convertibles built that year.

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Last edited by BDW; 09/23/21 12:56 PM.