A is 4, for ntp V4.
B is the major release number.
C is the minor release number. Even numbers are 'stable' releases and
odd numbers are "development" releases.
Following the release number may be the letter 'p' followed by a number.
This indicates a point (or patch) release.
Release candidates have -RC in the release number.
Here are some recent versions numbers as an example:
4.2.2 A production release (from the ntp-stable repository)
4.2.2p2 A production release (from the ntp-stable repository)
4.2.3p12 A development release
4.2.3p15-rc1 A release candidate for 4.2.4
Note that after the ntp-dev repo produces a production release it will
be copied into the ntp-stable and the cycle will repeat.
