Hi, Im using a polynominal equation for a last year thesis but have been having a problem.

I have used every polynominal order however none are giving me the correct answer which im using to compare with measured data in order to validate the polynominal equation is working correctly, it is not as you can see in my attached image i have used 10 as "x" however answer is not giving me the same answer as he measured data for 10.

how could i fix this issue? decimal places have already been increased but made no difference.

I have already imported the data on Matlab and used the polynominal function on there instead which did give an answer identical to the measured data so im just curious into what the issue with excel is?

Thanks