I believe they are saying that only the portion of premiums paid by UHG customers _that are not_ spent on paying out claims should be counted as UHG revenue. That is if I and my employer pay UHG $18,000 over the course of the year and UHG pays out $2,500 to my doctors and to cover my prescriptions, only the remaining $15,500 should be counted as UHG revenue.
The thinking here is that because UHG is legally obligated to pay out claims, this money only "passes through" their hands. I believe the legal obligation is the thing here.
Anyway, if these pass through costs (the claims they are legally obligated to pay) are removed from the equation then their revenue number is smaller and their profit margin is larger.