Multiselect, lists, single checkbox label erroneaous behaviour

1. In MailPoet I made one list calles “Newsletter”. MailPoet itself comes with a predefined list “My first list”. So I had 2 lists.

2. In GF I made a simple form: name, email and Mailpoet Newsletter field. In the MailPoet Newsletter field I set Multiselect Enabled to No. I wrote a label text in the Single Checkbox Label field. I want the user to see only one checkbox with my predefined label text. Checking the box should subscribe the user to the list I choose, in this case the “Newsletter” list.

3. When I update the form, the form shows two checkboxes with the two lists (“Newsletter” and “My first list”) instead of a single checkbox field with my own label text. On the front end there are also these two checkboxes. Multiselect is not disabled.

4. I tested the form on the front end by submitting it. Regardles whether I check the first or the second checkbox, in all cases the user gets a confirmation email with the list “My first list” checked.

5. In the Form entries this choice is not recorded. The Newsletter field is empty.

All this behaviour (3, 4 and 5) is not as expected. Am I doing something wrong?

https://wordpress.org/plugins/mailpoet-gravity-forms-add-on/