On the Helix all of the stereo delays (except the ping pong) have a true stereo path. The left and right sides are fully separate signal paths.
The delay time of the left side of the signal is set by the delay time knob/parameter.
The delay time of the right side is set by the scale parameter as a percentage of the left delay time. When scale is at 100%, the right side delay time matches the left side. Then, as the scale parameter is reduced, the right side delay time gets shorter on a percentage basis. For instance, let's say the delay time is set at 1 second. If the scale parameter is at 75%, then the right side delay time will be 750 ms (milliseconds). If the scale is at 50%, the right side will be 500 ms, and so on.
The reason this is done is because these stereo delays are often used for rhythmic effect. Having the scale parameter set the right side as a percentage of the left side allows for the delay timing between the right and left sides to stay proportional when the main delay time is changed.