Ok, so in chapter one she says she is 5 years old (twice no less) and in this chapter the prince is seven years old when he first meets her. So how is she four years younger than him?
The translation is a bit derp about it, but to put it properly
He was declared crown prince at 7.
There's a period of the king/queen looking for his fiancee that wasn't specified.
But doing a little math show it's 2 years: she's 4 years younger than him, she's 5, therefore he's 9
And consistent with that: They spent 1 year of the test period she'd be 6 and him 10 at the engagement reveal party.
And as page 26 say, 2 years later he's 12, she's 8.
#Math