Hello Desiree,
Unfortunately the CSS functionality in the document template is very limited and because of this it's very fiddly to get the styling right. I believe your CSS would work if applied to the span element rather than the table cell - which I don't think you can do.
You can try using a max-height with overflow hidden on the cell, however you need to be very cautious when forcing table proportions as you might end up with unexpected results.
For example: "max-height: 30px !important; overflow:hidden;"
Hope it helps.