We’ve a fairly new car with a similar system (that can be ignored/disabled thankfully). It seems to have both a some GPS/location based awareness of what the speed is meant to be that it falls back to as well as a camera based detection. I find it useful as a reference incase I don’t know what the speed is and missed the previous sign, but it’s also regularly wrong and not to be entirely trusted. For example the on ramp to the closest freeway near us it consistently reports as 10km/h when it’s actually 100km/h. I don’t know what it is about that sign specifically it can’t read as it looks fine to the human eye, but it would try to cap our speed on the freeway to >=90 km/h slower than the rest of the traffic (most are traveling slightly above) if we were to have the system enabled. As others in the comments have suggested it also can’t be trusted to get the speed right in school zones or for the correct distance for variable recommendations (e.g., speed bumps, roundabouts, etc.)