inaccurate colormap [FLIR TOOLS] in .jpeg thermal image

I am currently working on a project with a thermal datasets I found online. All I want is to detect the face using matlab and extract the temperature from the image, the images I got is in .jpg format, I tried to use the FLIR TOOLS to get the colormap.

Attached the actual image I got online, and the one with the colormap. As seen, the FLIR TOOLS detect that the temperature of the face is 74.7 Celcius at the highest, which makes no sense, is this possible to get the 'closest' value to? or it is impossible because the .jpg format? Can anyone recommend me on how to get the temperatrue from a Thermal image without the colormap? Thanks a lot!