Make and model of the amp would help.
If the amp has that kind of terminal setup you usually can't use more than one pair of terminals at the same time.
Also if you have 4 16ohm speakers in parallel connected to the 16 ohm terminal and common that may not be the best way to run them because those speakers would present a 4ohm load to the amp; not 16ohms.
Check the manual or the manufacturer of the amp.