Open one of the tabs in the top, and fill in all your data for 950 fps (weight, BC, range, zero, velocity, scope height, etc.etc.)....Open another tab, in input everything the same, except using 800 fps....Reopen the tab for 950 fps, and click on the box on the left of the other (800 fps) tab (a check mark will appear).... Both trajectories will now show on the graph, but they should cross at your sighting in distance (25 yds.)....Right click on the graph to open the menu.... Mouse over "Compare Trajectory Mode" and select "At Same Barrel Angle"....The 800fps velocity trajectory will now show below the 950 fps one, and you can see how the pellet will drop in comparison, without changing the sights....If you do this in the reverse order (starting on the 800 fps tab and click in the box on the 950 tab), the lower velocity will be shown sighted in at 25 yards, and the 950 fps curve will be above it....Bob