Unknown notation relating to stoichiometry I have never seen the highlighted symbol before. What is the name of the symbol itself, and what does it mean in this context?
It is probably supposed to be the 'corresponds to' sign[ref, p 105]; in this case simply representing that for every two moles of $\ce{NaOH}$ one mole of $\ce{H2SO4}$ is converted by reaction stoichiometry. 

This sign is difficult to typeset in LaTeX which is why I presume the authors used something else instead. Creating the sign is even more annoying in MathJax. The closest I [got at first] were 

$$\overset{\lower.5em\wedge}{=}\ \text{or}\ \hat{=}$$

which are $\overset{\lower.5em\wedge}{=}$ and $\hat{=}$, respectively.

Edit. After some testing, this option $\lower.1em\lower.5em\widehat{\raise.5em{=}}$ looks best in my opinion.

$$\ce{2 mol NaOH $\lower.1em\lower.5em\widehat{\raise.5em{=}}$ 1 mol H2SO4}$$

full code: $$\ce{2 mol NaOH $\lower.1em\lower.5em\widehat{\raise.5em{=}}$ 1 mol H2SO4}$$

Just the bare $\widehat{=}$ leads to

$$\ce{2 mol NaOH \widehat{=} 1 mol H2SO4}.$$



ref: E. R. Cohen, T. Cvitas, J. G. Frey, B. Holmström, K. Kuchitsu, 
R. Marquardt, I. Mills, F. Pavese, M. Quack, J. Stohner, H. L. Strauss, M. Takami, A. J. Thor. (2007). Quantities, Units, and Symbols in Physical Chemistry. ('IUPAC Green Book'). Third Edition. International Union of Pure and Applied Chemistry. (2008 IUPAC &amp; RSC reprint). ISBN: 978-0-85404-433-7. [free copy] 

Here is a picture of how it looks in the 'Green Book':