Question re upgrading from older version

[boxcleverliam]

https://github.com/Moneris/eCommerce-Unified-API-PHP/blob/3cd3f0bd5a92432c1b4f9727d1ca6334786d9066/mpgClasses.php#L20

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?