How much should i be paying for a

I called the manufacturer about the scaling question and they pointed out that it can be adjusted- there is a hole on the back of the unit that allows you to turn a tiny Phillips screw for calibration.
I knew that. Scaling was the wrong word to use, but I couldn't remember the right word then, nor even now.
What I meant was the divisions on the scale are so close together, and the mechanism in the factory tach is so slow, that
if you intend to shift at a true 5500, at what visual rpm do you actually shift at> Considering the width of the needle itself is like 100 rpm, and the mechanism could be another 200 rpm slower, are you gonna pull the trigger at 5200?
And then, with your eyes shifting from the road to the tach, and back, refocusing each time, who's actually driving the doggone car.
I mean my car hits 93 in the eighth, and I go thru 4 gears/three shifts to get there, and I gotta stay in my lane, with the tires on fire....... so I better be looking where I'm going. Bouncing of the rev-limiter is NOT the answer.
Jus saying
Daymn I just remembered the Word: Resolution. Getting old sux too.