Blown attic insulation slumps into the eaves unless a baffle holds it back and keeps the soffit vents open. The free wall-framing takeoff already worked out loose-fill depth and bags from a target R-value. It now also counts baffles: set insulation.attic.baffles and it gives one chute per rafter or truss bay on both eaves, using the roof's own spacing (truss spacing wins when trusses are used).
A 40 ft gable roof at 24 in on centre has 20 bays a side, so 40 baffles. A bay wider than the 22.5 in chute needs two. The count is checked by hand arithmetic only, not against a supplier's catalogue, and the takeoff does not yet model the compression of fill at the eave.