In the standard Firefly window on Pro 2012 the GC is in the bottom right corner.  Changing it to 1.0 may correct the differences to that you are describing but the subject is a little bit more complex than that.

I know the Bagginsbill has explained this in the past and in a way that I could not begin to emulate.  Having an understanding of GC is important if you want to get the best from the lighting in Poser 2012 or it least that is what I have found since I started using 2012.

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.