Maruti Suzuki India — Regarding stepny issue of baleno

What is the reason behind difference in the main tyres and stepny in baleno alpha 1.2
all tyres are of R16 size but stepny is of R15 size with warning dnt drive above 80km/hr.is this a joke or something.stepny is such a neccesity in car and you are doing this kind of thing and no one is mentioning this at point of time anywhere at the time of inquiry or purchase.got my tyre blasted for some reason few days back then only it came in to my notice.and i was alone in night with no shop open to get the new tyre so had to drive long with the stepny tyre only keeping in mind that cnt drive above 60kmpl on this alone horror road.this is realy ridiculous.