Andy should have buttoned up. Otherwise he looks great.
How to button a 2-button single-breasted suit jacket.
When standing, button only the top button.
When sitting, unbutton the jacket to allow it to drape more gracefully. Never button the bottom button; doing so will keep the suit from draping properly around your waist.
3 or 4-button single-breasted jacket.
With a 3-button jacket, always button the middle button, and optionally, the top button. Again, unbutton the suit when sitting down. Never button the bottom button; on some 3-button suits, the hole will not even line up with the button.
On a 4-button suit jacket, always button the middle 2 buttons, fasten the top button if desired, and never fasten the bottom button. Unbutton the suit when sitting.
From top to bottom button the rule is "sometimes, always, never"