What does the notation '2/10 net 30' signify in terms of sales discounts?

A 10% discount if paid within 2 days, with a total of 30 days allowed for payment.

A 30% discount if paid within 2 days, with a total of 10 days allowed for payment.

A 2% discount if paid within 10 days, with a total of 30 days allowed for payment.

A 2% discount if paid within 30 days, with a total of 10 days allowed for payment.