With 2D sonar you are reading a cone straight down from the transducer. The size of which depends on the depth of the water, the deeper the water, the bigger the cone. Only if the boat is moving, will returns on the left of the screen been behind you, if moving forward.
The left side of the screen is history, and the right side is closer to real time, or what is under the transducer right now. The vertical bar on the far right of your Garmin is called the A-scope and works similarly to a flasher, or a real time sonar. The number at the bottom of this is the diameter of the sonar cone at that depth, I can't make it out in your picture but it is there. If you turn the sensitivity up and the scroll speed to fast, you will be able to see your jig on the graph and all of what I just said will start to make more sense.