Typically, that third number is smaller than the second, i.e. the interactive desktop heap is larger than the non-interactive desktop heap.
The solution is to modify that registry setting to increase the third number of the SharedSection parameter, i.e. increase the size of the non-interactive desktop heap.
For example, you could change this:
SharedSection=1024,20480,768(My setting)
to this:
SharedSection=1024,20480,4096
You must re-boot the server for the change to take effect.
Regarding the warning at the top of this document: if you make one of these 3 heap size settings too small, the server may not have enough resources to start.
