You will only see the dark water column...
35' SI Range means the unit will only display return echoes from within that 35' distance away from the xducer...
In your scenario of 35' SI Range...If you took a 35' rope and attached one end to the xducer...and then swing that rope in a semi-circle from 35' horizontal right to 35' horizontal left...every echo within that semi- circle would show on the display...(within the upper reaches of the selected SI beam frequency)...
Every echo outside of that semi-circle would not be shown on the display...
Setting the HB SI Contour mode to "On" would show a blank screen with no echoes anywhere because you told the unit not to show echoes closer than 35' Range with the Contour Mode setting...in addition to setting the SI Range setting at 35' told the unit not to display echoes farther than 35' Range...
Rickie