The way it currently works is: when a new user onboards and creates a plan, enters some data, and experiments with the app, plan data and results are kept on the client side and not transmitted. Calculations are performed in the browser, and data disappears on refresh. If the user upgrades to Premium, they are then presented with a choice of several data persistence options, including Cloud Storage, LocalStorage Only, and Manual Import/Export. Plan data is only stored server-side if the user enables that option.