The system uses the 'user defined multiplication factor' method of diameter calculation when the result from the 'Navy Table look up' method for bundle dimeter calculation returns a value that is less than the diameter based on the total CSA of the wires with no air gap. i.e. gives a value that is technically impossible.
The Navy Table look-up method utilses the average wire diameter in a bundle and it has been proven to be very reliable when there are many wires with diameters that are all the same/are very similar, however this can start to become erroneous when the average is reduced by the presence of significantly different sized wires in a bundle.
So we detect when the Navy Table cannot provide a valid result and then switch to using the user specified multplication factor as the next best methid instead.
So I would expect that if you analyzed the content of the bundles you mention that they would have disparate sizes of wires and may also have only a few wires in the bundle.
Hope this helps,