Hi,
You are right, it is not visible due to the following reasoning:
Whether or not the optional checkbox is checked is not displayed in the subscribers table because it can have a different value after each form submit. The data recorded from the optional checkbox is the time at which it was first checked (and submitted). This is the moment a visitor opts in. Any subsequent optional checkbox values are not relevant to record for determining the opt-in time. Therefore the opt-in time can be found in the “Opt-in Time” column in the subscribers table.
If you want to check whether the optional checkbox has been checked for each form submit, you can see this in the notification email (if enabled).
Kind regards,
Team Download After Email