Different manufacturers will have different attenuation factors for their coax and different types of coax will have different attenuation factors, that's just one example of a "typical" coax. It's easier to just use 5.5 or 6 dB/100' or 15-20'/dB as a worst case insertion loss for coax and be done with it when calculating a signal loss budget. Unless you have a very long cable run that will require tilt compensation, it's not worth the effort to use the whole chart.
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