Changing the 'Required space' number

I'm using ZipDLL to install the main file (because it's very large -- see other post). The content of that file, however, does not get included in the 'Required space' figure which is given as 0.0KB, but should actually be 2.2GB (!)

Is there any way I can set that value manually or just stop it from being displayed?

Thanks 🙂

AddSize.