I don't know how you can do that with this prosumer software.
You can reduce the bit rate to get more on the disc. My suugestion is to download Power2Go 15 day trial trial. It has a smart fir feature that will automatically reduce the bit rate just enought to fit.
If you are selling the DVD and blu rays, consider looking at putting you videos on a thumb drive. Most people can play the video through a USB connection on computerss/TV,/Game Console/etc. A small memory one is only a couple of bucks so it you are selling them, you may have to adjust your price.
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BoilerPlate: To posters who ask for help -- it is nice to thank the volunteers who try to answer your questions !
Anything I post unless stated with a reference is my personal opinion.