Additional attributes | -> List | -> Export

I need some help.
For a statistical evaluation, I have created a field for additional attributes in the invoice form and selected as the field type “List”.
The manual says that there must be a number in the list before each entry, followed by a comma followed by the corresponding entry.
So something like this:
1,car in blue
2,car in green
3,car without a roof
etc.
While entering the invoice, the entries in the list are also without numbers, as it should be.
If you select the Supplementary Attributes field and export it, for example, as an Excel file or CSV, the actual entries in the export list are not, but the numbers in front of the entries.
I can not imagine that’s how it should be?

Is that a mistake in Dolibarr?