methratio.py memory issue

[Nitin123-4]

I am running it in slurm with : srun --nodes=1 --cpus-per-task=20 --ntasks-per-node=1 --mem=30000M

methratio.py -I --np 10 --mem 5000 -o SampleName_methratio.txt -d $genome_fasta bam.bam > SampleName.bam_mr.log

but I am getting the error : Only 3158 MB available, not 5000

As i am blocking 30gb memory I am not expecting this memory issue. Please help with this.