This is referring to the amount of travel in the trigger. If you watch the trigger when you squeese it from the neutral position there is much more throw to the throttle side, and a little to the brake side.
Like this... TTTTTTTTTTTNBBBB T being throttle, N being neutral, B being brake
Your M11 is a high end radio. It's set at 70/30. I don't think you can get it to go to 50/50. You'll find the 50/50 on RTR radios that have reverse.