Dihedral around 1663,1669 not found in topology. Using mult=3

GROMACS version: 2020
GROMACS modification: No
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Dear all,

I have completed a protein simulation without a crash (40 ns), I am trying to extract rama information from the protein by using “gmx rama”, however, this notes pops up:

Dihedral around 870,880 not found in topology. Using mult=3
Dihedral around 884,897 not found in topology. Using mult=3

I checked the atoms 870 and 880 are both hydrogen atoms, and it is true for all the information that pops up. Therefore I have 2 questions pop up:

  1. Why is this happening? In my previous experience, this note never pops up
  2. what does multi=3 mean? how will this affect the rama scatter plot?

I am using the OPLS/AA force field and nothing unusual when I visual inspect the trajectories through VMD. Thanks for the help.

Best regards,