There are few things that might confuse you:
- There are 2 types of PoE - one is passive, and the other is 802.3af/at. Passive PoE is 18-28v and 802.3af/at is 48-57v. Switch will automatically detect if device supports PoE.
- This switch/router comes with 28v power supply, so out of the box your 802.3af/at connected devices will not be powered on.
28 V 3.4 A power supply is already included in the box. There is secondary DC jack on the back of the enclosure that supports 48-57 V power supply (not included, can be purchased separately - product codes 48POW (1.46A 70W) and 48V2A96W (2A 96W)).
And lastly, from my own experience, you don't need 28v power supply at all. Connecting only 48v+ power supply is enough to power up passive PoE and 802.3af/at devices. :)
TL;DR buy one of the mentioned power supplies and you will be good.