Peter, you've made a minor math error. That's a Delta T of 41.5C, (25C ambient down to -16.5C), so that looks to be operating within specification. Looks like its working fine.
Glad to hear that. SGP does not think so since I selected -20 ambient, and it warns me that its only is -16.
Ok good, nothing to worry about then. If SGP doesn't know how to measure the air temperature around your equipment, it won't know what the AMBIENT temperature is. For some observing software, it pulls it from a Davis Weather Station, an ASCOM device such as a observing conditions hub, a focuser, or other air temperature source.