Need help with CFD

I am working on a school project where I am trying to compare CFD values with wind tunnel testing values. My lift and drag CFD values are smaller than the wind tunnel data. Does anyone know if the empty spaces in this pressure contour is the reason why my numbers are similar?

I did an enclosure and symmetry in design modeler. Then used face meshing.

https://preview.redd.it/frd6q2zoqvtg1.png?width=1605&format=png&auto=webp&s=65be491bfed02ca58ed0c30e6c3c19dd747745a1