As quoted from David Pogue:
‘Software version numbers are pure marketing concoction. The upgrade from System 7 to System 7.5, for example, was a baby step compared to the leap from 7.5 to 8.0. If anything, it’s the tiny increases that really count, because that’s when a program goes from “4.0” buggy to “4.0.1” usable.
Of course, then there’s the numbering leap from Word 6 to Word 98. That one seems about right.’