In the case of ATK, the Base ATK is the sum of the Agent Base ATK and the W-Engine Base ATK.
The "Combat" stats are buffs which are triggered only during battles and cannot be seen in the character page included with the other stats. They can only be observed if you check your stats during combat. They will be written in green text and summed up with other similar stats. These stats are usually found in W-Engines and 4-Pieces Drive Disks effects.
Unless the enemy is stunned, the Stun% will be 0%. When stunned, the bonus will differ based on enemy type. Small and elite enemies usually have a 100% bonus, while bosses usually have a 50% bonus. Some agents can increase this multiplier while an enemy is stunned.
Credits
Writer: arkkus
Formulas and Data: Dimbreath, arkkus, Carrier5by5, Kyle, 666bj