The setting will tell you how many minutes you can expect to fit on a standard DVD-5 when you adjust the average data rate. Maximum bit rate will not effect how many minutes will fit on the disc. You may want to do a one minute test of a complex part of the video (lots of motion, pans, etc) to see what it will look like. You could be disappointed with the quality.
The alternative would be to make a dual-layer disc but unless you are having them manufactured vs. duplicated playback compatibility could be less than desirable with DL+/- media. Studios almost always make dual-layer discs (manufactured from a glass master at a replication facility) to ensure that the highest quality encoding can be used and will fit on the DL disc.