DDR2 data rate and data bus confusion
You have it right.

This is the "raw" or "peak" transfer rate that you get within a single burst of data. The actual long-term throughput will be somewhat less because of the overhead associated with starting and stopping bursts. However, if the memory controller is smart about interleaving operations on different "banks" within the memory chip, it is possible to get sustained throughput that's very close to the peak value.

With multi-chip memory modules, you simply multiply the numbers for a single chip by the number of chips, since they simply operate in parallel.