5 (five) Business Days
Some contracts have a style where any numbers which appear are repeated as words – “You must do this within 5 (five) Business Days”. I really can’t see the point of this drafting. Either the “5” and “five” are the same or they aren’t. If they’re the same, the repetition is redundant. If they aren’t (“5 (fourteen) Business Days”), someone has made a mistake. There is no way to tell which (in this example, of 5 and fourteen) is correct, so it simply makes a poor situation worse – having the wrong number in there is probably better than having the clause being void for uncertainty.
Rather than re-write numbers in words, just use one and take the time to check it properly.