From now on, public preview versions will have odd numbers while beta versions with full features have even numbers.

For an example:
1.0.21 - preview
1.0.22 - beta

This is due to strange policies of Apple's store which made it impossible to publish another build of 1.0.20 to TestFlight users once 1.0.20 became a public release. Other than the documented beta vs preview differences, the two versions released together will be identical.