figure this one out

i have some text, no formatting (plain times new roman, size 12)

i create a new style, with only a font and size 10

i select the text, apply the style, it applies the font, but not the size

i change the style size from 12 to 8, the text change to size 8
i change the style size from 8 to 72, the text change to size 72
i change the style size from 72 to 10, the text change to size 12

any ideas?