It's not a "tracking" number, even the highly subsidized China Post charges a lot for that kind of service.
More likely it is either a Delivery Confirmation number or a simple shipping invoice number.
This is not a problem.
You have confirmed that the item was mailed. It will take an easy minimum of 20 days to arrive and more likely a full month.
If you have not received the item by Day 40 after purchase, start a Item Not Received dispute through the Resolution Centre.
If the item arrives while the dispute is open, inspect the item and if it is satisfactory, close the dispute. This will not harm the seller. Since the seller shipped promptly, he still gets good marks for shipping time, btw.
If the item does not arrive, close the Dispute and get your refund.
If you get a refund then the item arrives, you can repay the seller through PP's Send Money option.
You have a full 60 days to leave feedback.
One caveat- if the seller offers to send a replacement, politely insist on money. Replacements from overseas have all kinds of problems. Money is easy.