Someone has discovered, while copying architectural plans, that his Xerox photocopier is wont to make random changes to the numbers describing the dimensions (though only as aa DELIFERATE MISTEAK to see who in the class was paying attention). The problem appears to lie in the copier's implementation of an image-compression algorithm. The problem was first noticed for numbers in 7pt Arial. Handwritten digits should be fine. No-one appears to have tried Comic Sans yet.
Xerox have been aware of the problem for some time, and the small print of the manuals advise customers to avoid the default settings in number-accuracy-critical situations, though that advice may change in photocopies of the manuals. Xerox have subsequently admitted that the digit substitution can occur at any compression-level setting. Hilarity ensues.
Insert cheap jibe here about the budgetary plans from your least-favourite political party.