Currently the font-sizes in the CSS of the blog are controlled via the EM sizing method instead of FIXED pixel (i.e. 11px).
This has caused some issues with font sizing because different skins set default font size of the body, and when that is set to small size to begin with, the EM sizing will reduce it further.
I will change the CSS of the module in the next version (03.05.00), but for now, you can simply change the font-size attributes in the CSS file to fixed pixel (i.e. 11px).
This will solve your issue for now.