Say, for example, $50.0-49.6=0.4$. Does this result have $1$ significant figure, or $3$ (as in the data: $50.0$ and $49.6$)?
Had it been $50.0-4.6$, it is understood that the answer is $45.4$, by the rules of significant figures. How do I apply them in the "$50.0-49.6$" case?
This question deals with $50-49.6$; so a related but not the same question.