It is the VersionInfoVersion
directive that you need to set. The reference describes this directive as:
Specifies the binary file version value for the Setup version info.
Here is an example usage of this directive (but of course in real you will most certainly prefer to use some version information from your application instead of constant):
[Setup]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program
VersionInfoVersion=1.2.3.4