Appointments+ CSS

I was trying to troubleshoot why the header in the "My Appointments" row was so thick. Though I am quite daft with CSS, it looks to me like the CSS being used to render this table is using ".header" to render the table headings, though .header is inherited from the theme and cannot be modified without also affecting the (page) header of my site, which I do not want.

(see screenshot)

Is there an easy fix to force Appointments+ to render its table with its own header element so that I can reduce the thickness of the table header row without affecting the rest of my site?