They have 2800 employees with 5-10 reports per manager.

At 8 layers of management (so 9 layers total, with the bottom rung being non-management), 3 reports per manager comes out to 6561 employers on the bottom rung. At 5 reports each, that 8 layers would give you over 300k at the bottom, an 10 each would give you 100m at the bottom.