USPS Priority Mail tracking?

I bought an item from eBay and I feel funny about the whole transaction. None the less, I received a tracking number today for USPS Priority tracking and it begins with 0309 and has 20 digits. All my other purchases using USPS tracking numbers begin with 9101 and are 22 digits long. The seller usually sells antiques...this was a snowboard jacket. No other items on his store are clothing...just antiques. The communication has been less than stellar but some sellers are like that. The seller told me the item would be shipped on Monday but it was marked shipped today...with the delivery date of today or tomorrow. Anyone know if USPS tracking number start with 0?