The scale between lines is logarithmic, not linear. Halfway between lines is not 5. You cant judge what it is. So you then cannot take that wrong reading and interpolate values from the FC/CYA Chart.I'm not 100% with the rounding up crowd for cya just yet. I'm still struggling with an old school tfp mindset tho. I think you can tell the difference between 55 and 60 in the tube, and it will allow you to SLAM at 2ppm less fc.
Garbage in, garbage out.
Trying to shortcut the SLAM Process is what leads many to frustration.