Taking into account of the significant figures, what is the value of 9 . 99 m – 0 . 0099 m ?

In subtraction the number of decimal places in the result should be equal to the number of decimal places of that term in the operation which contain lesser number of decimal places.

$\frac{\begin{array}{c}9.99\\ -0.0099\end{array}}{9.98}$

$\Rightarrow 3$ siginificant figures