Custom style anomaly

I have a custom style and the only thing I set for this style is the font size. Any size would do! But when I set it to size 12, nothing happens. In fact, the “Style Attributes” on the right sidebar is EMPTY whenever I set it to 12. Anything above or below 12 will show up in the style, for example: 12.1 but just not “12’

I checked all the styles in the document and none of them have “12” for font size, except this custom style that I made. Anyone know what’s really going on here?

I notice that size 12 is the default for the style when you create it. How come this default can’t be applied?