Upload numeric value fails

Generally upload works. But one numeric attribute gives me trouble.

Error: Value 32 for Attribute Length does not exist in the list of valid Item Attribute Values for Item PLAA5ss32

The attribute Length is defined as

In the Excel spreadsheet it is entered like

There are so many different length that I decided just to make it from 1 to 1000 instead of defining every length individually

The to range is 1.(dot)000,(comma)000. Is that right?

That is correct. ERPnext formats it like this.

May I suggest that there is something wrong with the upload procedure on the server. After multiple failures -
I created a item manually on ERPnext. Then I exported it to an .xlsx file. Deleted the items in ERPnext and uploaded the exported file straight from my Download folder without opening it. - Failed!

Nothing is working. I am trying since yesterday evening to upload some items with a numeric variation.

Uploaded the artificial feet in different sizes and this time ERPnext accepted the items. But only the variants, not the template the variants belong to. How is that possible?