Any automatic transmissions utilise hydraulic accumulators to reduce the rate at which pressure gets applied to the internal clutches and bands when a new gear is selected. In some transmissions, such as the Toyota A340, the back side of these accumulators are all connected together and have a pressure regulator to control the transmission fluid pressure on the back side of the accumulators. This gives the ECU some control over the rate at which the pressure gets applied when selecting a new gear. A high back-pressure results in faster and harsher shifts, and a low back-pressure results in slower and smoother shifts. Note that slow, smooth shifts are achieved by allowing a lot of slip in the clutches and bands in the transmission. Too much slip, especially under heavy load, can result in excessive wear. 

Output Frequency - This sets the frequency used on the output. Toyota A340e uses 300 Hz. 

This table will typically be filled out in the base map supplied by Haltech (see Importing a Transmission Base Map). 
If you're using a transmission without a base map, then the Toyota A340 base map might be a good place to start. Simply import just the Accumulator Back-Pressure Duty Cycle table. 

Note that most transmissions utilise a pressure relief valve, so the pressure decreases as you increase duty cycle.