The authors of The Mark fail to make this important distinction. In the novels, Carpathia is obsessed with the number 216. They have yet to explain why this is, but it is evidently supposed to correlate in some way with 666 without being too obvious. In the novel, the loyalty mark is a biochip with 216 or a number related to it or the name of Carpathia tatooed on one's hand or brow. Equating the mark and the number of the beast is an exegetical blunder.
Space forbids a complete examination of even some of the leading theories among brethren.
We will summarize these and refer the interested reader to other sources for further study. In the ancient world, numbers stood for letters. Courier Publications, pp. West, op. cit. I once studied with such a man.