I know all that; was just keeping it simple.
VBR (variable bitrate) settings
VBR: variable bitrate mode. Use variable bitrate modes when the goal is to achieve a fixed level of quality using the lowest possible bitrate.
VBR is best used to target a specific quality level, instead of a specific bitrate. The final file size of a VBR encode is less predictable than with ABR, but the quality is usually better.
Usage: -V(number) where number is 0-9, 0 being highest quality, 9 being the lowest.
Switch --- Target Kbit/s --- Bitrate range kbit/s
-V0 --- 245 --- 220...260