99Instances2Go I tested your capx and there is a small innacuracy compared to the formula (around 15 more pixels for a 900 pixels jump if I am not mistaking, which is about 1.7%, on Edge it seems to be varying more sometimes, but that may be my computer), I agree it is not that big but we do not know how accurate the OP wanted to predict it, I am also in the latest stable.
We actually discussed that difference in another topic and ashley suggested a solution to the issue but does not seem to have it implemented yet.
(also sorry that you had to take time to figure out the formulas, I know those are not that easy to calculate)