The green circles show the location of the key (notch) in the PCI connector that determines which voltage card it will accept. You cannot put a 5 volt card in a 3.3 volt slot. The universal cards are keyed so that they will fit in either voltage slot. The Dialogic cards are 32 bit, but will work in the 64 bit slot, they just don’t use the full width of the PCI bus.
This card only has one notch in the PCI edge connector, and will only fit in the 5 volt PCI slot.
Notice the 2 notches in the PCI edge connector. This is so the card will fit in either the 5 or 3.3 volt PCI slot