what is "number of slots/discrete devices" ?

When use megawizard to generate ddr2 controller + altmemphy for cyclone 4 E, I found a option "number of slots/discrete devices" in tab of board settings. The only number is 1. Does it mean that cyclone 4 E can not be used for dual dimms every one ddr2 controller?

Another option is total memory chip selects in tab of memory settings. As we see, the maxim number is 8. Every dimm only has 2 cs#, so what dose it mean that the number 8 in memory settings?

I used quartus II ver.11