This picture should give you a good idea on how you should adjust the return system.
Unity gain, means you adjust the gain and tilt at this amplifier, so you get the same input level and bandwidth at the next amplifier. Do not forget you need to adjust the return system at the optical NODE first and the amplifier after. The return input signal between 5 to 40 MHz should be between 15 to 20 dBmV at each return input. Below that you wont get high enough Carrier to Noise and higher than this you won't have enough signal leaving le cablemodem.
EXPLANATION of 15 to 20 dBmV input at the return input of the NODE or each AMP.
30 dB loss with first multitap + 6 dB for the drop + 5 dB for the splitter + 15 dBmV input = 56 dBmV level require at the output of the cablemodem.
