NTP uses A.B.C - style release numbers.
At the moment:
 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.
Feel free to suggest improvements...
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