I am having a problem in reproducing the bader analysis result of the paper that I read. In the paper they studied charge transferred in a 4X4 Be-doped graphene, and found that beryllium transferred 2e to the carbon atoms in the system.They used VASP software to implement the calculation. I have tried to reproduce the result following their computational details but I am getting 1.56e. I am using VASP Medea 5.3v which is pretty easy to use.  The following are what have been doing:

1) First I did geometry optimization  using their parameters

2) Next, I loaded my optimized structure and did single point calculation while the bader analysis flag is turned on. After this step, I checked the output file for the result.

I have repeated step 2 by increasing NG(X,Y,Z) but still getting the same result. Please what are the steps to follow to get the right result using VASP MedeA?