Burning to a BD-R 50GB Disc

Hello all!:cool:

Im trying to burn to a 50GB BD-R disc. My issue is, what I'm trying to burn which when I check the properties says that it's 48.1GB in size burn ImgBurn states that the files are too big to burn? I don't understand why that would be the case when the disc is 50GB. Can someone assist? :confused:

Thanks