a 32 bit binary number can represent 2 to the power 32 = 4,294,967,296 bytes. Divide by 1024 into KB and then again into MB and then again into GB and you get the result = 4GB.
My understanding of running 32 bit on a 64 bit os is that it defaults to 2GB limit however you can build it with a flag set allowing for most of the 4GB to be used, so it depends if Cubase 32 bit was built using that flag - I would hope so