The above measurements are based on measuring one side of the garment to the other when the garment is laid flat. 

How to Measure (PJ top):

For accurate measurements, wear a tight vest or your underwear.
BUST: Measure around the fullest part of your bust, with your arms relaxed by your side.
WAIST: Measure around the narrowest part of the waist.
HEM: Measure around the fullest part of your bottom.