MKL no of threads vs no of processor

I am trying to do some more details analysis about parallelism options/optimization in a dynamic application which uses PARDISO for the solution of a sparse linear system. This simple usage dates back more than 1 year. Now I am trying to find if a dynamic set up of the maximum no of threads can lower the total elapsed time so I added the following statements:
!
      nt = mkl_get_max_threads()

 On the workstation used for development: Intel(R) Core(TM) i7-4810MQ CPU 2.80 Hgz the functions returns 4.

On the C++ windows driver which launches the Fortran application with PARDISO the system functions:
GetSystemInfo(&SysInfo) ;
    numCPU = SysInfo.dwNumberOfProcessors ;
returns for numCPU a value of 8.

Any explanation ?

Regards

Luigi Raimondi