Max Special Damage Score (MSDS): This is a score that estimates damage dealt per move gauge usage (of the attack that has the highest score). This value is proportional to the actual damage dealt, but not identical. This is calculated via:
Max Special Damage Score = [ (Sp.Atk * Power/100 * Accuracy/100) ] / Move Gauge Cost
Where Power, Accuracy, and Move Gauge Cost are for the move that have give the highest score, and Sp.Atk is the Max Sp.Atk stat for the Sync Pair as seen in the Dex.
Note this does not consider any buffs such as Sp.Atk boosts or passive skills.