Since the switch itself is un-managed, it will act as a hub. What this does is take the full available bandwidth at the WAN side, and divide the data flow by how many different devices are requesting data. The JGS524 should work as a gigabit device to expand your network without having to get down a dirty with networking.
Say you had two machines, each machine has gigbit capabilities, and are of equal quality (performance wise), each machine is trying to draw a one gigbyte file, the available bandwidth (depends on your specific ISP package as well it it's quality); then the full available amount of data would be theoretically split between the two machines, and the downloads would theoretically finish at the same time, give or take.
Again, theoretically, each machine would have a path open to the tune of 100Mbps at full throttle, in a perfect world.
With good wiring and a solid ISP drop (wire from the port outside) and a late model computer, I would be satisfied with an average of 180Mbps, and peaking to 210Mbps on seldom occasions.