Blackwidow Elite: How can I use hypershift (FN) with F1-F8 keys?

Hi, i think the better question would be: Why am I not allowed to set an secondary function with the FN key in combination with the F1 - F8 keys in synapse, like with nearly every other key on the keyboard? ... I understand why im not able to change the hypershift-function of the F9 - F12 keys, cause its already in use, but I really don't understand it for the F1 - F8 keys. can someone pls explain? thank you very much (sorry for the bad english, not a nativ)