It's pointless quoting sizes close to the maximum capaicty of a disc in GB, we need it in Bytes.
Put the disc in the drive, load ImgBurn and switch to 'Write' mode (write image file to disc). Then copy + paste all of the disc info from the box on the right.
That'll allow us to tell you if you've already got the maximum capacity available to you on your BD-RE or if you need to reformat it. Once's it's formatted to maximum capacity you can try and build/burn your project again. The 'Information' tab in 'Build' mode will tell you the exact size of your project in bytes.