Can someone help me clarify something....

Bleeding Wound (Ex): At 11th level, when the gunslinger hits a living creature with a firearm attack, she can spend 1 grit point as a free action to have that attack deal extra bleed damage. The amount of bleed damage is equal to the gunslinger’s Dexterity modifier. Alternatively, the gunslinger can spend 2 grit points to deal 1 point of Strength, Dexterity, or Constitution bleed damage (gunslinger’s choice) instead. Creatures that are immune to sneak attacks are also immune to these types of bleed damage.

This skills says it does ability bleed damage but my DM is saying that it just does one ability point of damage on that round and that's it. Surely bleed damage is continuous, even with ability points? If I'm right and it is continuous, how long does it last for? Is it limited or just until it is healed with a heal check/spell?