See here: creature_template (3.3.5a) - TrinityCore - Confluence
There is a base calculation based on level + rank + class, but you can modify the stats using the following columns:
Code:
HealthModifier
Used to modify the base Level/Class health of a creature. This field comes from WDB.
ManaModifier
Used to modify the base Level/Class mana of a creature. This field comes from WDB.
ArmorModifier
Used to modify the base Level/Class armor of a creature.
DamageModifier
Multiplier for mindmg and maxdmg
Example: mindmg=200 maxdmg = 500 DamageModifier = 10
Outcome: mob will hit for 2000-5000