This is just an example:

Let's say they have a W2-G for $20,000, but their actual cumulative total winnings are $50,000 (each individual win counts, even though there is not a W2-G for the smaller amounts), and their cumulative total losses are $53,000.

In that example, you are supposed to report $50,000 of gambling income, and then you enter $50,000 of gambling losses on Schedule A.