The cylinders that Max Dog sells for this purpose are 2.8 liters, so 10 liters should be more than enough. You'll need to check the pressure to make sure there's enough gas. Usually for a full cylinder the pressure is around 2000psi, but in your case it wouldn't need to be completely full. I'm not sure what the atmospheres measurement is for though.
In some countries the cylinders are measured in liters, not cubic feet. This is not the same as the number of liters of nitrogen it contains. For example, Max Dog sells 2.8 liter cylinders which contain 400 liters of nitrogen when full.