There is an optional Asset Approver role that each TUB can decide to implement or not.  The Asset Approver workflow step will be invoked based on a combination of object code, amount, and role assignment:

The object code must be in the 6800-6821 range
AND
The total requisition amount, not just the amount allocated to those certain object codes, needs to be equal or greater than $10,000
AND
There is an assigned Asset Approver for the TUB

The additional approval step will appear between Level 4 and Level 5 approvers.