Take a look at page 9 and 10 there is a table with Agent Version numbers that are different if you upgrade from 7.5 HF3 to HF4 or when you upgrade from 7.5 HF1 or HF2 to HF4?
Note:For Deployment Solution, if you upgrade from ITMS 7.5, ITMS 7.5 HF1, or ITMS 7.5 HF2
to ITMS 7.5 HF4, then the plug-in upgrade to the new version that is mentioned in the column, Upgrade
version in 7.5 HF4 of the table. If you upgrade from ITMS 7.5 HF3 to ITMS 7.5 HF4, then the plug-in
version remains same as that in 7.5 HF3
Network23
PS: In my mind it is really confusing if the above table is true, because than you never know if you are running 7.5 HF3 or an upgraded version from 7.5 HF3 to 7.5 HF4!