What is the excused limit for a Light Impurity (like cow or goat urine) on a garment or body limb?

Excused Limits of Impurities and Wiping/Sprinkling Rules

• Up to the size of a dirham coin.
• Less than one-quarter (1/4th) of the affected garment or the affected limb.
• Up to half of the garment.
• Only up to 3 drops.