What is the function of "DVD-5 disc size" in the "Advanced Setup" window?

You can set the size of the target DVD-5 disc. Adjusting this value will affect the compression rate. Please do not exceed the DVD±R/RW's biggest capacity that you bought it. The default value is 4387MB. (Note: The size of 8.5GB or 2.0GB should be set under the direction of our support team.)