correct that is the disk speed.
After you go into the make your own DVD option click add your own video files (or something similar, im at work and dont have the software, it is the 2nd or 3rd option down the list on your left)
Then you click [...] or [browse] and select the video file/s you wish to encode for dvd.
You may have to have a dvd-r to burn for your dvd player.
In AUS we have to use dvd-r to burn for PAL encoded dvd's (this is only because of our TVs and dvd players)
I believe you (americans?) use NTSC but you can use either dvds, i think.