We can only offer him up to the value of the option we declined, which was about $4M. (I don't recall exactly, it was $3.99M or something.) That is regardless of cap space or MLE or anything else. Doesn't matter how much we can offer other players. We are not allowed to give Giles a raise relative to what his rookie deal would have been, because other teams abused that loophole in the past to give their players a raise before their rookie deal was "over".
I think that would help the Kings retain him this summer, if they can.