Perhaps you have noticed the 4 Ohm and 8 Ohm print on the speaker terminals?
These are only to indicate that the tweeter is an 8 Ohm speaker when you are Bi-wiring the speakers by removing the jumpers between the upper and lower speaker terminals.
This is mostly done in a stereo setup where you want to use bi-wiring speaker cables.
You can also run the speakers Bi-amped with one amp connected to the tweeter and one amp connected to the rest of the drivers on the lower speaker terminals.
It is most common to run the speakers with the jumpers on and a single wire to the speakers for either home cinema or music use.