readme update

README.md

@@ -121,6 +121,16 @@ generate a whole genome _de novo_ assembly for serran
 supernova run --id=serran --fastqs=x_dir/ --localmem=470 --maxreads=298666666
 ```
 
+refine maxreads parameters :
+- To calculate the number of reads that you need, first start with an estimate of the genome size : 792.000.000 bp
+- Next, set the number of reads so as to achieve 56x raw coverage. This is (genome size) x 56 / (read length). 792.000.000 x 56 / 150 = 295680000
+
+```
+supernova run --id=serran --fastqs=x_dir/ --localmem=360 --maxreads=250000000
+```
+
+
+
 ### 2. Generating phased genome sequences
 
 Once serran's assembly has completed, we generate a FASTA file representing your assembly.