Basically, the Flasher displays the same data as the RTS (Real Time Sonar) window on your sonar display. Just that the data is presented in circular display. You do not get to see the old data like you are used to seeing scroll across the screen, only the Real Time Sonar of whats directly under the transducer at that moment!
I have included a page from the ICE Flasher manual that shows the typical flasher display.
Robert