Update slurmtopbs.md

docs.it4i/general/slurmtopbs.md

@@ -15,7 +15,12 @@ The `qsub` always starts execution in the `$HOME` directory.
 ## Migrating PyTorch from SLURM
 
 The Intel MPI provides some useful variables that may be used in the scripts executed via the MPI.
-these include `PMI_RANK`,`PMI_SIZE` and `MPI_LOCALRANKID`. For example:
+these include `PMI_RANK`,`PMI_SIZE` and `MPI_LOCALRANKID`.  
+
+- The `PMI_RANK` and `MPI_LOCALRANKID` returns the process rank within the MPI_COMM_WORLD communicator - the process number 
+- The `PMI_SIZE` returns the process rank within the MPI_COMM_WORLD communicator - the number of processes  
+
+For example:
 ```
 $ mpirun -n 4 /bin/bash -c 'echo $PMI_SIZE'
 4