Thanks mardel:
I understand that the 4 is part of the name of the program.
Back on 2014-04-04, at this same SoS page URL, Print Maestro was offered, and the version number at the right of the page showed that it was version 5.1.1 (I saved the content of that page). I captured all of the screens when installed. When the final program came up, it stated Print Maestro 4, so I do understand that the 4 is part of the name of the program, then for that program name, they have released different version numbers. In my installed copy of Print Maestro, if I go to the Help About dialog, it shows version 5.1.1.
Since they gave away Print Maestro 4, version 5.1.5 in 2014, I wondered why they are now offering version version 1.0.6 of Print Maestro 4 (out of order). I wondered if they might have made the program name Print Maestro 5, but they had forgotten to change the number at the top of the display. If they had, I can understand that it would have a new version number series.
To add to the confusion of how they do their version numbers, on the SoftPedia page for Print Maestro, the version number is 1.0.6852.42784 but on the Changelog tab, it lists a Print Maestro 2.6 from March 13, 2008, and at the bottom of that 1st Changelog page, is a link to “READ THE FULL CHANGELOG,” which also includes a Print Maestro 2.5 (May 18th, 2006).
The Softpedia pages seem to indicate that at one point, the name of the program might not have had a number, but did have version numbers, or the 2.6 and 2.5 might have been part of the program name, but if so, the version number was not stated. That is why, I am trying to figure out what type of numbering system they are using.