I know there are significant pronunciation differences between ancient Greek, Byzantine Greek and modern Greek. In modern Greek "d" is pronounced like a voiced "th", similar you the "th" in "than". So the Greek "two" is pronounced "theeo"; "delta" is spoken as "thelta". "t" is pronounced like a short "d", so three is "dria" and "h" (which is written like an "X") is pronounced like the "ch" in "loch", so seven is "chepta", which does bear some similarity to "septa". Another difference is that the Greek letter "b" is pronounced as a "v", so "beta" is pronounced "veeta".