Function fields in Zoho CRM

Function fields in Zoho CRM

I would like to use Zoho function fields in CRM. Setting-up the function is pretty easy. But I do not see any value in the field when I select a specific field.

When setting up a function-field I get a weird warning message at the begining. Unfortunately, I have no idea what it says, because its translation into German is totally wrong. Any ideas what to do to get the function field working?

Thanks in advance.