There are 3 instruments shown.
- A Condar probe thermometer on the double-wall stove pipe.
- The stovetop temperature on a Sandhill thermometer
- A digital probe readout for the flue using an Auber AT100
IMHO - the only one that matters is the stove top (2). Because that is what is mostly heating your space.
The others simply show temps of flue gas, which can be quite high even at startup (and especially at startup since then the most air is added). But that really mean little. As startup flue gas temps do next to nothing to heating your space with a double walled stove pipe which you seem to have.
So exactly... what was the point of this post?