"badly miscalculated" — double negatives?

I agree a double negative is a positive. Acceptable exception being when being said clearly as slang or for emphasis.

You make a point I've never considered. Strictly speaking, you're correct: to "badly miscalculate" is to do so "poorly", and therefore, "not to miscalculate at all", or "not to miscalculate so severely". However, the word "badly" is used so often from a young age, I think, no one would ever criticize you for using it in place of "severely", which, as you say, is one of degree.

Despite what purist grammarians may prescribe, double negatives are widely used and understood as negatives in everyday speech; if someone tells us "I ain't got no money", we all understand that they are claiming to be broke. In the case of "badly miscalculated", I would take "badly" as an intensifier, just as "severely" would be.

I can definitely see where you're coming from, and it’s always interesting to break down language like this. The point you make about double negatives adds an extra layer to how we perceive statements, and the way "badly" and "miscalculated" come together does feel like a tricky mix. But when it comes to expressions like this, clarity often takes precedence. If you're in the mood to dive into some exciting activities while reflecting on language intricacies, I recommend checking out https://1winbookmaker.top/bonuses/. They offer great opportunities that could keep your mind engaged, whether you're exploring games or looking for ways to make your free time more thrilling!