Yes... precisely. Honestly they can be tuned properly with right matching component in action but... for whatever reasons, none of unit I have received for modification (over 15 now) has ever shown anything within reason (beyond 10c typically). I won't say froster is totally free of it either on the one MrDeeds is using either... that one reads off quite often too but could be warmer or colder lol...I think his unit was off by about 2-3c... he can confirm it with k-type probe embedded there with proper reader.
Lately, I've been using k-type probe enabled LED controller for such display of temp which is within +/- 0.5c of fluke I have.
Here is an example of what you can laugh on. The unit on my fluke goes down to -60c with no load for some time until compressor warms up. (vapochill LS modification).
Basically, it will go down to -73c than can't read further so goes into this than next thing it just doesn't understand that temp is that cold and acts as if thermal reader is borked
The only time it reads somewhere close is 0 to 35c range... still with some errors. The problem intensifies around -15c down. So in essence your negative temp could be off as little as 10c to as much as 20c depending on individual unit.