A version number is built from 3 parts, x, y and z and given as x.y.z. x denotes the major version number, y denotes the minor version number and z denotes the fix number. x starts from 1, y and z start from 0. If z = 0, it isn't included in the version number.
The major version number is increased when a new concept
is added. The minor version number is increased when an
existing concept is improved. The fix number increases
with every bug- or security fix.
The fix number is reset to 0 when a concept is changed
which inherently corrects all fixes. The minor version
number reset to 0 when a new concept inherently includes
all improvements.
This thus means that a x.0 version is quite unlikely,
at the time of writing, version 1.3.2, not version 1.3,
is in development.