Version number scheme:
Stable major release: x.y.0.0 (In strings: "x.y.0")
Stable minor release: x.y.z.0 (In strings: "x.y.z")
Development version (e.g. trunk): x.y.99.0 (In strings: "x.y+1 dev")
Development releases: x.y.99.z (In strings: "x.y+1 Alpha/Beta/... z")
x.y always refers to the current stable version. x.y+1 is the upcoming major version.