Yes, from .23 all the way to .30 is .07 versions skipped correct?
Version numbers aren't usually linear that way. Typically each digit, or maybe each pair, constitute a series of revisions within a larger revision block. So for instance with the DF numbers:
0.31.06
The 0 refers to the major version. This is alpha, so Toady is still working toward the first version.
31 refers to the major features (arcs, bloats, whatever system he's worked out). Going from 2D to 3D was an increase of one in this count. Between releases, there might be 3 or 4 major additions, so it might jump from .31 to .35. To Toady, this is a linear increase as he's got .32 and .33 and .34 versions, but they weren't released.
06 refers to the minor features. This is like the one above, but these usually increment approximately with each successful build. Again, not every one may get released so it could jump to .08 if .07 was problematic.
Each developer has their own way of doing this. Knuth is using pi for his versioning for TeX so his current version number is 3.1415926. The next release would be 3.14159265. Each release adds a digit. Version numbers aren't even slightly user-friendly - they're entirely for the benefit of the developer.