Whatever the quota.... That might be one way, but certainly the other way is for the government to make a decision. Then there's a debate in the House and a resolution to hold a referendum. There's a vote in the House, and it says yes, we want to hold a referendum on this particular question, and the question is there. I think this would be a very legitimate way of deciding what question to put, other than a constitutional one, even though a constitutional one is also the object of much consideration by Parliament, in both houses.
So this is the way I would see it.