From Dark and Darker Wiki
In case of Poisoned Weapon you have stacks you can apply to an enemy. Do I just multiply the stacks by the base damage like so: Total Damage = Stack Count * Base Damage * (1 + Physical Power Bonus * Attribute Power Bonus) + Additional Magic Damage * Attribute Power Bonus
Example calculation(At 5 Stacks Poisoned Weapon): Total damage (before debuff duration) = 5 * 4 * (1-.17 * .5)+10 * .5