You should be combining data. The driver needs to say conclusively what the kart is behaving like, then you need to correlate that experience to the tire temp data. You then make a change, test again, record new data, and evaluate how that change affected the data.
For example, it cannot be conclusively said that the kart was oversteering or understeering simply by saying the rears were higher than the fronts. If your front tires never reached optimum temperature you could experience an understeer as the tire would not properly adher to the surface. Conversely, your situation could be as TJ described. The front tires reached optimum temperature but the rears were overworked as a result of an oversteer and actually went beyond optimum temperature.