Wrong minimum font size

In the administration menu, I've set the parameters to limit the font size between 12 and 24 pixels. No line height adjustment. Using Firefox 3.0.5 on Windows XP, increasing and decreasing works. Except the smallest font size it will go to (as confirmed in Firebug) is 13.52 pixels.

Looking at the code, you're increasing by a factor of 1.2 times the default until you hit the maximum specified font size. And you use 0.8 to decrease it. Instead of using factors and decimals, maybe just increase in even whole number steps based on the distance between minimum and maximum? This way you don't get any fractional font sizes and it will always be able to return to the lower end of the scale instead of being stuck a fraction above it.