Does the calculator’s estimate change if I increase the number of floors later?

Yes, and more importantly, if you already anticipate adding a floor later, your foundation and lower-floor columns should be designed for that eventual load from the start, since retrofitting stronger reinforcement into an already-built foundation is far more disruptive than planning for it upfront. Re-run the calculator with the higher storey count and discuss the implication with your structural engineer before finalising your current construction drawings.