Invoice terms 2 net 15

I received an invoice for $30,000 under the above terms. I've never seen this before. I'm familiar with 2/10 net 30, etc., but am wondering if the vendor intended to this. My interpretation was that we get a 2% discount if paid within 15 days and have no idea when it would be due if we paid in more than 15 days. I paid $29,400. It's a marketing agency, so there is a decent chance somebody thought this sounded like accounting language...