Just remember, use its reading as additional info to be compared to your own good judgement.
That said, testing accurately in the oven doesn't always mean that they will read accurately on the stove top. In the oven, the temp is even all around the unit if you set it on a rack. If you stuck it to the side, then it's probably hotter on the face of the thermometer than the rear. On a wood stove, it will set on a hot surface, with cooler air above it.
Also, of the 3 rutlands I owned, 1 was a complete piece of poo. The second, read well up until about 550 degrees where it was reading 50 degrees off. By the time it said 600, it was 100 degrees off, and the problems got worse from there. That unit started getting sticky, so I got another rutland which did the same thing as far as being inaccurate after 550.
Because of this error, I placed it not on the hottest part of the stove, but a section of the stove top that read about 100 degrees cooler than the hottest (I knew that because of the IR thermometer) . By doing so, the thermometer could be used, (and understood by the wife) in that when it hit the maximum rated burn temp of 550, the hottest part of the stove was actually about 650-700, which meant the wife knew things were too hot.
pen