It's the opposite of strawman.
A strawman argument is a weak argument to justify a position you disagree with; its purpose is rhetorical: It's meant to make your position look strong to onlookers (and perhaps to yourself).
A steelman argument is the strongest possible argument you can come up with to justify a position you disagree with; its meant to help you find the truth by taking seriously the people who disagree with you.
OP is using the word slightly differently than normal, in that the position OP disagrees with here is, "Docusign needs 7,400 employees". A strawman would be, "Docusign needs 7,400 employees because it needs to show the stock market that it's a serious company" -- weak and easy to demonstrate that it's stupid. A steelman would be, "Docusign actually needs that many sales people and customer service reps."