[gmx-users] inconsistency in xvg file

[Dhrubajyoti Maji]

Dear GROMACS users,
                    I am using gromacs-2018.3. My system is molten
acetamide. Run time is 50 ns and sampling frequency is 20 fs. I have
calculated MSD from gmx msd command. The msd.xvg file initially contain
timestep of 0.02 ps but from 10000 ps it looks something like this:
   9999.96     19.9453
   9999.98     19.9458
     10000     19.9464
     10000     19.9469
     10000      19.947
   10000.1      19.947
   10000.1     19.9467
   10000.1     19.9464
   10000.1     19.9461
   10000.1      19.946
   10000.2     19.9459
     and so on upto 50000 ps. I can't  understand why is this happening and
how it is affecting my result?
Can anyone help me?
Thanks and regards,
Dhrubajyoti Maji