The muscle imbalances (imbalance between functionally opposite muscle groups such as abdominals and back) are calculated using two opposite muscle groups and their maximum forces (e.g. abdominals and back extensors). The app shows you exactly which areas you should improve in to create an ideal ratio for your body.
Please note: The ideal ratio is not always 1:1. Due to anatomical conditions and usual loads, this ratio differs for certain body parts.