Write something like \max_X as an inline mathjax equation. The live preview will show it with the X below the max. This is the formatting resulting from a \displaystyle equation. In fact, when the card is actually seen (also simply through the preview via ctrl-l), the equation is correctly displayed with the X not below the max, as inline equations usually look.
In other words, it seems like the live preview always shows equations with \displaystyle, even when this is not the case.