Zigbee - optimal signal

What are the optimal signal strengths I should have for my zigbee devices ?

Check out the docs: Zigbee Logs - Hubitat Documentation

To summarize, they suggest that an LQI under 200 indicates a high error rate, and an RSSI closer to 0 is better than one farther away ("approximately" -100 is the lowest value, and what they don't say is that in the real world, you're likely to get values much closer to that than 0...in their screenshot, all of theirs are in the -70s, and I have many in the -80s without any apparent issues; if I'm interpreting the values correctly, anything above 0 would mean the signal got amplified, which seems highly unlikely despite +127 being their "approximate" highest value).