Bought a Ps3 Fat with 3.60 and PKG Installer

Hi,
i bought a Ps3 fat and it got the Firmware 3.60. The funny thing is, it also got the PKG Installer. So tried to install Multiman which worked. but when i start it ill get a black screen.
Does it mean that i got a retail 3.60 Firmware? How can i check it? System Informations says 3.60 only

I hope you can understand it all. My english is not the best :)