The result of a measurement is $57.64$ $\pm$ $0.38$ (for the sake of simplicity, I omit the measurement unit). I would know which are the certain digits in $57.64$ $\pm$ $0.38$. I know that $57.64$ has $4$ significant digits. According to the rule
the significant figures in a measurement consist of all the certain digits in that measurement plus one uncertain or estimated digit
I should say that $57.64$ $\pm$ $0.38$ has $2$ certain digits, in particular they are $5$ and $7$. But, if I rewrite $57.64$ $\pm$ $0.38$ as the interval $[57.26; 58.02]$, I see that the only digit that remains the same is $5$. Therefore, is it still possible to say that $7$ is a certain digit ? What is the definition of "certain digit" ?
Thank you in advance.