Enhancement: Symptoms, on (1 Injury Done)

[Sunrunners_Fire]

Symptoms (1/3 HP Injury Done), *3
Symptoms (1/2 HP Injury Done), *2
Symptoms (2/3 HP Injury Done), *1
... are the official values. If I wanted to have Symptoms apply its' effects upon doing any injury at all, what would be a fair value? (I'm leaning towards *4).