not sure about the numbers on the package, but I believe their should be some label saying it's an upgrade. There is no difference in upgrade and the full version in that the upgrade is a full version as well except that it will ask for proof of previous edition before it will install.
Are you buying from the Adobe Store? The package WILL state whether it's the full, an upgrade (see Phil's comment), or the eductional version.
Are you buying from a certified reseller? The package SHOULD give the full details.
Are you buying from eBay? Who knows what you'll get, or whether it will work?
Are you buying from an individual? Other than asking them, and trusting them, I'm not sure that there's a way to tell. Maybe a certain UPC on a clean shrink-wrapped box could yield a clue.
Note: if you need a key-gen, or similar, for the installation key and for a S/N, it will certainly be bogus. I realize that you know this, but I felt that I had to include it for any others.