SW2017 SP5

We do not do a lot of weldment drawings here, so I am not all that familiar with the inner workings of cut list tables. 

I have a cut list for a tubular frame with some feet made from plate.  I have the plate set up as a weldment profile.  In the model, the tree looks like this:

The plate items are detailed on a separate sheet of the drawing.  I would like to replace the length value in the cut list table with N/A but cannot figure out how to do it.  When I right click on a cut list item and select Properties, the Cut-List Properties dialog is displayed:

Changes to the LENGTH property in the above tab have no effect. If I select the 'Properties Summary' tab, I can change the property value, and it seems to stick:

But, the cut list on the drawing does not show the change:

Also,when I view the cut list properties again, the Properties Summary has reverted back:

So, is what I'm asking not possible, or have I missed something?