The fastest scroll speed. You want the quickest screen updates so you see your presentation and fish in real time. Only the very first row on screen pixels on the right side is real time. All to the left is recorded history so it makes no difference what it looks like.
If your unit has a vertical flasher on the right edge, that is real time also.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1