The version e.g. (9.5.28) with 3 digits is a RELEASE.VERSION.FIX where:
Release: is a complete new generation of the application with Major functionality changes.
Version: is with major functionality changes but fewer changes than Release.
FIX: is just for fixing some rare occurred errors or bugs or performance improvement (some minor functionalities may be included)
We usually schedule regularly the updating for all customers who have System updates subscription and their Accounting Status is STABLE for all of new RELEASE or VERSION.. As for the Fixes, we usually do not upgrade them if we did not see these errors or low performance cases for companies unless they request that literally from us.
You can check all versions deatils from time to time to know "what's new" from this link http://www.hybrid-solutions.com/forum/forumdisplay.php?26-Release-Notes