HFSS based simulation of current does not match theoretical analysis

I am trying to calculate current from the current density in HFSS via fields calculator. I used Ampere law to get current. However the value of current I get is not the same as in theory.
My model is a dielectric cylinder and I am trying to calculate current flowing through it.

Kindly advise.

Thanks

There could be lot of factors on what the cause of the discrepancy is. Its easier to tell where the problem lies if you can provide more description on how you are setting up your HFSS model.