Can I safely put a PCI-E 6+2 cable into a 12v4 slot on Enermax 1000W PSU?

I have an Enermax Revolution87+ 1000W PSU.

It came with a total of 6 PCI-E 6+2 cables. (and some other cables, but that's the one I need information about)

The red 12v4 slot, which appears to be the same as the other two that are plugged in, but they are listed as 12v2 and 12v3, is empty.

Would I be able to effectively use the power supply if I were to buy an additional PCI-E 6+2 cable and plug it into the 12v4 or does the 12v4 imply more than the location of the slot?

I wouldn't want to fry the motherboard by trying to generate too much power to it.