The ruling on concluding a contract after throwing a stone by saying, "If the stone reaches such a place, I will sell it to you for such a price"?

Question : He says to his partner, the buyer: "I am offering a price for this stone; if it reaches such a place, I will sell it to you for five percent."

Answer : There is nothing preventing this; that is, there is nothing wrong with the contract after the throwing. However, no one does this except that there is something wrong with it, yes. Do you see? He wants to finish the counting; it is the counting that determines what he wants.