Question re upgrading from older version

[boxcleverliam]

eCommerce-Unified-API-PHP/mpgClasses.php

Line 20 in 3cd3f0b

'API_VERSION' => 'PHP NA - 1.0.22',

1. What does "NA" refer to here? (North America? New API?)
2. How does this series of version numbers relate to the older 2015 version of mpgClasses.php which has a higher number? (like this: 'API_VERSION' =>'PHP - 2.5.6',)
3. Would it be correct to assume that the ~2015 version of mpgClasses.php was the starting point of this repo in 2016, and that a new numbering system was adopted at that time?