In Takeoff reports, the Qty column on a takeoff (assembly) row adds up the Qty of every item under it. When the items have different units, that number means nothing. For example, a wall with 2.61 sheets of plywood, 0.20 carpenter days shows a Qty of 2.81.
The “Aggregate up to” dropdown only offers All levels, Folder, and Takeoff. None of those stops the sum at the takeoff row (parent).
Can you add a column setting to hide group totals on the parent? That way takeoff, folder and group rows can show blank instead of a mixed-unit sum.