In contrast to the experience OklAAhoma had, I had a true e-Voucher. Had an email with a voucher number. I could look up the value, and I could simply apply it at payment time just like a gift card. No agent (or confusion) required.
Now that you mention it, the email (or rather the lack of an email) was part of the confusion. The agent we spoke with about redeeming the credit kept insisting we should have received an email, with value stated, just as you describe. We received no such email.