Age is just a number.
Could you tell from someone's body how old they are based on purely their body looks? No.
Someone could look more mature for their age body wise, and vice versa, someone could look less mature for their age body wise.
It really is just a number.

You could be more mature than your age, or less mature.
It could go either way.

Your age does not define who you are or how you are.
I know for a fact that I can go both ways.
My soul is much older than my age.
But my heart is much younger than my age.
My mind is just a bloomin' mess!