urgent!!!: layer break in a dlt

hi, i'm authoring a dvd wich has 6.5 gb so it should fit in a 4.7 dual layer dvd.
i have a dlt7000, encore is finding the dlt, my troouble is how do i tell encore how to use layer break? i already assing dual layer 4.7 in proyect settings but it keep saying the space in the medium is not enough, and the option to use the layer break in the build dialog is grey...i need to do this urgently, thanks a lot

thanks, i got the point and solved the issue