Unable to change length in weldment cut list

Hi, I've been trying to manually change the length for one of the cut list items for weldment that I have made.

The item is a bend RHS, so the actual length is less than what it says on the cut list.

I have tried right click that cut list item and go to properties, failed to change the length. It just changes back to the value regardless what I typed.

Couldn't find anywhere else that I can possibly change it. Any help?

Thanks

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