DxDatabook: empty field replaced with 0R value

I have a table with a numeric field (Z100MHz) that represents the impedance of ferrite beads components. I checked the "Show Unit for IEC62" and added the field to "Use European for property" textbox on dxdatabook option. For some item the field is empty but when i load the table inside DxDatabook i see "0R" value.

Why?

Thanks