In the vinegar you can put as many as you, the more you add the more vinegar you'll have to add and the more cycles it will take before everything is dissolved.
You could put as many as you got in vinegar wait till bubbles stop showing when you shake it, then take the liquid out and use it with your plants and simply add vinegar to the remaining shells.
You could put as many as you got in vinegar wait till bubbles stop showing when you shake it, then take the liquid out and use it with your plants and simply add vinegar to the remaining shells.