Hello! I was able to reach a contact in Xeon EP/EN Product Marketing and below is the explanation provided:
Slot per channel = DIMM slots available on the server board per memory channel
DIMM per channel = DIMMs populated in the available slots per memory channel
2 Socket server board with E5-2650 with both CPUs populated.
Each CPU support 4 memory channels, and each channel supports 2 memory slots
Hence total 2x4x2 = 16 slots available.
Slots per channel = 2 in this case.
However, out of the 16 slots, only 8 are populated, 1 DIMM in every slot for every memory channel of the CPU, and the other 8 slots remain unpopulated.
In this case, DIMMs per channel = 1.