Font Size Issue

Before I started a scene, I changed the font size from the default to 12 and set the double-spacing. As I’m typing, I realize I’ve forgotten something, so I insert a sentence between two paragraphs. While doublespaced, the sentence was set to size 11.

And, because the size looked wrong, I highlighted it. I think I must have picked up a bit of the line above or below because Scrivener simply told me it was 12, when it was clearly not the same size as the rest of the text.