what does (2 ohm + 2 ohm) mean for subs?

When i looked at some alpine tyre - R subs that im going to power with a rockford fosgate 501s 2 ch amp, i noticed that they said that their impedance was (2 ohm + 2 ohm) does that mean that my amp is only going to put out what 4 ohm ratings are? Does it matter if i wire it in parallel or not? I know it sounds stupid but I am buying the amp from a friend and if it is only going to put out what the 4 ohm rating is than i dont want it but if it puts out its 2 ohm rating then i do. So i need to know! Bad! Any suggestions are helpful!

that means it has a dual 2ohm voice coil setup, and it can only be wired to 1ohm or 4ohm

1ohm - that amp will hate you and it will eventually die, if it even works at all
4ohm - it will put out the power that it's rated at for a 4ohm speaker