What does $"\frac{2}{10},\frac{n}{30}"$ mean with respect to cash discounts?

Select one:

$2$ out of $10$ deliveries will be delivered within $30$ minutes

Deliver $2/10$ths of the order on an $"$n$"$th day of the month

A $2\%$ discount if paid within $10$ days or net due in $30$ days