Surely when you scan the speed it is the position of the speed line relative to the bug and the trend if visible that you are looking at and not necessarily the digits themselves?
Absolutely spot on; and is true of all the magenta bug displays. Is the a/c white performance speed/hdg/alt lined up with the magenta cmd bug? Quick & easy to ascertain at a glance. In B732 I had to fly 210, 190, 170, 150kts etc for the various flap settings. Now on NG I just fly the green F bug which is high;lighted by the CMD bug. Simple easy. Am I + or - not a specific number.