The box of 15 is popularly known as Panchadashi Yantra in which a set of nine boxes is there. On the boxes numbers are mentioned in such a way that total from all sides is fifteen. The following Shloka explains the answer for the box chosen against the query-

Ekam cha dhana labham, Dwitiya cha dhana kshyam, Tritiya mitra sanyuktam, Chaturtha cha kalah priyam, Panchame raj sanmanam, Shashte karya nashnam, Saptame dhan dhanyam cha, Ashtame maranam dhruvam, Navame raj sanmanam, Hutva kevli bhashitam.

For getting an answer for your query, repeat the question in your mind and then click on any one of the box ("Kostak") after closing your eyes. The result to the query will immediately appear on the screen.