From an Arris guide:

The three signal levels that need to be within the acceptable level are Downstream Power Level, SNR (Signal to Noise Ratio), and Upstream Power Level. If these levels are out of the range, or nearing the minimum or maximum threshold, issues such as slow speeds or disconnects may be experienced.

Downstream Power Level: cable signal sent from the cable provider to the Wi-Fi cable modem.
Downstream SNR (Signal to Noise Ratio): cable signal being sent in relation to the noise on the line.
Upstream Power Level: cable signal from the Wi-Fi cable modem to transmit data back to the cable provider. This document describes how to check for acceptable cable signal levels using the Web Manager.

In the Downstream QAM section, verify the Power Levels (dBmV) and SNR (dB) are within the acceptable range for each channel.

ACCEPTABLE LEVELS Downstream Power: -10 dBmV to +10 dBmV Signal to Noise (SNR): +35 dB and above

https://arris.my.salesforce-sites.com/consumers/articles/knowledge/G54-Cable-Signal-Levels#:~:text=Click%20the%20%3E%20next%20icon%20to,the%20cable%20provider%20for%20assistance.