This integer is the live internal-enclosure temperature reading in whole degrees Celsius, capped at 100, taken from a sensor inside the switch chassis. It gives an admin a numeric trend to graph over time rather than waiting for the binary atiOverTemperatureAlarm to trip, so gradual creep, say from 42C at night to 61C during a hot afternoon with the HVAC down, can be caught and acted on before it reaches the alarm threshold. Polling this every few minutes and alerting on a sustained value above roughly 55C is a common way to get ahead of the overtemperature alarm.