[AlphaCommerceHub] What are the possible values of the `PayerDetails`.`Custom2` field of a response to the PayPal's `PaymentStatus` API request?

It contains the customer’s email address in my case: a PayPal’s PaymentStatus API request, and a response to it.
What are the other possible values?
The «PayPal October 2017» specification does not answer the question.

The buyer email address. This is documented in our offline PayPal guide.

@Steve_Rivas can we check as sample PaymentStatus is missing from online documentation and that included the note on this field