[HdS84]

999 or 9999 etc. are extremely common in traditional statistics, especially because there is no known good sentinel value. In many cases I wished that they used the maximum value as a sentinel, e.g. take 255 for a short as invalid and make only -244 to +244 normal numbers.

[addaon]

As someone else who regularly uses 8.93 bit words for computations, I understand completely.