As you can see in the screenshot above, when a customer selects this option on the form the window expands to advise on what we require in this circumstance, and also clarifies when this should be selected.
Lastly, if you have already created a payment or subscription for the customer you will see a grey dot against these. If clicked on to view in more detail, a message will show at the top of the screen advising that the customer's mandate requires multiple signatures and they haven't yet completed the process.
If you have a customer whose mandate has remained in this status for a couple of days, it may be worth reaching out to them and asking that they check their email account for their dual signature paper mandate to sign and upload. If they can't find this email, ask them to get in touch with our support team who should be able to get a new one sent out to them.