Yah, I think they assume it is one of those "if you are going to use this, then you know what you are doing" things. Most PoE installations use large PoE switches to feed the power to many IP phones or cameras in a building. The voltage is industry-standard, IEEE 802.3af.
I'm not using it now, but I did successfully use the TP-Link injector on my 1032 phone, so you'll be fine.