When creating a custom field some datas are tested while they are hidden

Administer-> custom datas, create a test dataset
Add a field :
choose a name, choose alphanumeric as type and advanced multiselect, enter one option like : testlabel/testvalue
choose reference to contact in place of alphanumeric (the select option you configured is hidden), validate and you obtain :
"Please enter a valid number"

The problem is due to the testlabel/testvalue where testvalue should be an integer.
1 - in the original choice (alphanumeric) nothing forces testvalue to be an integer
2- this value is hidden so it's hard for the end-user to detect what's happening

Maybe some cleaning is needed