I got five steps from the Old Senior and added one soul method or the last step. After I added the final step the proficiency of the array improved by a lot. But then I discovered another flaw in the seal formation. The Six senses step that the Old man taught me in the beginning had a big flaw in it.
According to my research the whole Soul Devouring Seal should have ten steps to make a perfect array. But the Old Senior had the knowledge of only five steps and after three months of trial and errors I added the final step.