What does the R and L mean on a cnc mandrel tube bender?

What does the R and L mean on a cnc mandrel tube bender?

Assume that the bending machine is in good condition. Look for the marks "R" and "L", and "0" and "45" on them. If you start measuring from the left and want to bend 90 degrees, tilt 0 and set the measurement mark on "L". If you start measuring from the right, add "R".