The flow rate goes down about 12% for every power level at the selected distance based on the pump's model.
Using the graph located in the product page: http://www.coralvue.com/diablo-dc-3500-variable-speed-water-pump
You would be able to compute the following:
Based on the DC3500 pump curve:
At 0 horizontal inches on power level 6 (full power), the pump pushes 924 gph.
At 0 horizontal inches on power level 5, it would push approximately (924 - 12%) or 813 gph.
At 0 horizontal inches on power level 4, it would push approximately (924 - 24%) or 702 gph.
At 0 horizontal inches on power level 3, it would push approximately (924 - 36%) or 591 gph.
At 0 horizontal inches on power level 2, it would push approximately (924 - 48%) or 480 gph.
At 0 horizontal inches on power level 1, it would push approximately (924 - 60%) or 369 gph.
The same concept would apply at different distances and with each of the corresponding 3 pumps.
These are NOT pressure rated pumps. These pumps are not ideal for second floor applications or to feed Beckett or downdraft skimmers where consistent pressure is necessary.