User Configuration > Policies > Centrify Settings > Mac OS X Settings > Dock Settings > Adjust the Dock’s magnified icon size
Set the level of magnification to use for items in the Dock. If you enable this group policy, icons in the Dock are magnified to display in a larger size as the pointer moves over them. The valid settings for Dock magnification range from 16 pixels for minimum magnification to 128 pixels for maximum magnification. The default size is 80 pixels.
If you do not configure or disable this group policy, icons in the Dock are not magnified when the pointer moves over them.
Once enabled, this group policy takes effect when users log out and log back in.