Difference in Input U value and average-calculated U value in Part L

Hi,

I have the difficulty to sort out the non compliance of Wall U value. I have just used the single type of Wall with 0.27 in U value. However, the calculation results shows the U(a-calc) of wall is higher than the U limit and different from my input as well.

I have checked the input data in Data reflection report and i cant figure out where is the problem and no clue how to solve it. I check the 'surface where the maximum vale occurs' in Data reflection report as well. but i couldnt see where the U(a-calc) come from.

Thanks

Brian