The pack contains a total of 3 sachets of 5g each. You can use 5g to make yoghurt from one litre of plant milk. Afterwards, you can also inoculate with the finished yoghurt instead of a new yoghurt culture. Simply take 2 - 3 tablespoons of the finished yoghurt and add it to your milk instead of the yoghurt culture. This works up to 10 times, after that you should use new cultures again.
This way you get up to 30 litres of yoghurt in total with the package.