Solved! Go to Solution.
As ttokoro already noticed - somehow the "R" in the definition of your variable W is not labelled as "Variable" but rather as "Constant" and so its interpreted as the built-in molar gas constant.
You can tell it by the different (green) color.
Its not sure how or why Primes autolabelling failed. Sometimes wrong labels are applied when you edit a region multiple times.
Solution, as ttokoro already wrote, is to manually label this "R" as "Variable" so your variable R is used for the calculation and not the predefined constant. The color of the "R" should turn from green to black (if you did not change the default color settings).