One of the most common uses of 'promotional value' is to sell gift cards at a discounted price, either directly on your site or through discount sites like Groupon and Tuango. The value of the card is set at the actual amount received and the promotional value is the rest of the value.
Example 1: You sell a $200 gift card on your website for $150.
Result: The monetary value of the gift card is $150, and the promotional value is $50.
Example 2: You sell a $200 gift card through Tuango and the customer pays $139 for the card. Tuango takes a 25% commission.
Result: The monetary value of the gift card is 139*.75= $104.25, and the promotional value is $95.75.
When you look at the reports, you see a breakdown of the "real" value and the "promotional" value. The promotional value and the "real" value are used at the same rate. For example, on a $200 gift card, if a customer spends $100, $50 of "actual" value and $50 of "promotional" value are deducted from the card.
Please note that you should check with your accountant as to the appropriate method of accounting for such transactions. In the province of Quebec, for example, you can record the promotional value as income and (marketing) expense at the same time, giving you a "net" income of $104.25 in the example above. You can either record Tuango's commission as income on the day they invoice you, or as the gift cards are used. Please check with your tax advisor.