One of the bolts is a spare. So, use only one bolt to attach your Deeper smart sonar, and keep the other in your tackle box as a spare.
Moreover, please make sure you are using the right attachment position for the line, to ensure the stability of the device when it is reeled back. When you fish from the dock or bridge, screw your attachment bolt to the middle hole. Use the bottom one, if you're fishing from the shore. It is important that your Deeper does not tilt when trolled. When it tilts, it scans the water surface rather than the bottom, therefore causing connectivity and readings issues.