According to the instructions written on my bottle by my Vet, 1mg per kg. Repeated fortnightly (or monthly, a second Vets advice) for three treatments.
Treating worms is a little like treating mites. The first dose takes out the worms, not the eggs, you need to repeat the dose later to get the recently hatched wrigglies.
I was told to use it three times, perhaps two would be sufficient. Maybe a time honoured keeper can answer that?