وإن وجدها زائدة فالمشتري بالخيار
Translation: If it is found to exceed the stated quantity, the buyer has an option.
This is unlike the surplus in a lump-sum cloth sale. Once each cubit has a separate price, an additional cubit can entail additional consideration.
The buyer is neither automatically entitled to every extra unit at the old aggregate price nor forced to pay more without a choice. The following words state the available alternatives.