^Well it is something that he famously repeated many years later in interviews
My speculation on the matter is that MJ was drawing on what he knew about aircraft designations and marrying that to a serial number format. The Flying Fortress could be viewed as the 17th bomber design (B-17) and its variants were appended with letters (B-17G, for example). While I am aware that format is similar but not the same, it is not a stretch by any means to see its influence in what he derived.
Based on that interview, then could it be that for example NCC-77832 is either the 778th design, 32nd bird or 77th design, 832nd bird? I figure at some point, they could have built more than 99 Enterprise-type ships and the 100th bird would be NCC-17000 ?
It's an interesting thought from MJ though.