That essentially means your computing `c / x`, which is incorrect. By passing a constant you're skewing the what was a linear relationship. For example, say a benchmarks compares at `300ms` vs `600ms`, and say we use `fn(n, m) = (n - m) / m` to compute performance regressions. So `fn(600, 300) = 1`, but if you do `fn(1/600, 1/300) = -0.5`.

Or is there something else I'm missing here?