Are you using this page to login to the Manage option ?
The article you list though is about something else.
The OS it self is updated with incremental updates on a periodic basis.
For instance OS 10.4 had updates that finished at OS X 10.4.11
Mavericks is yet to have it first update and is ay OS X 10.9
Mountain Lion (OS X 10.8.x) got as far as OS X 10.8.5
i.e. it is the last number in the three number sequence (the 11 and 5 in the updated versions listed above)
Upgrades are the version number after the 10 and have the name associated with them such as:-
Leopard (OS X 10.5.x) Snow Leopard (OS X 10.6.x) through to Mavericks at OS X 10.9
These have mostly been paid for Upgrades. (Mavericks is Free)
iMac 2.5Ghz 5i 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad