Can someone plesase demonstrate how to use this new Decarb Formula?

I found a new decarboxolation formula via a link in another reddit post.

Standard widely used formula to determine THC remaining post decarb: 0.877*THCA + THC,
this one I get. GG#4 with 20% THCA, 0% THC, 1 gram (1,000mg) .2 x 1g = 200mg THCA
post decarb: 200mg * .877 = 175.4mg Total THC.
New formula: (0.877*THCA + THC)/ (Product − 0.123*THCA)
I attempted to use this, but I'm flaunting my ignorance here as I just did not get a sensible result.

To all you Mathletes, thank you in advance!