As I said its testing the PIXEL size barrier. even though its capitalized or not a FONT pixel system has a static size for cap or non cap what mirc is testing is the cap of it's size.

Search up Pixel Size on google or some other string im sure youll find what I mean,

Ill try again to explain it a tad better, when you write something in a font size the size becomes the barrier for that text weather it be 16 pixels (14p text) 1 pixel bottom 1 pixel top space.

If you ever designed a banner for a website you might learn more about pixels this way