Shipping label with both UPS and USPS tracking numbers?

Hello everyone, this might not be the right place to ask about this but I just recently bought a UPS ground saver shipping label through the site Pirateship. On the label, it has both UPS surepost and UPS parcel select tracking numbers on it, both of which seem to be valid when I try to track them on the UPS and USPS websites.

My question is: can I safely ship the package through USPS since it also has a USPS tracking #? I don't want it to get delayed if they have to send it back to me. Any help/insight is appreciated!