[d_burfoot]

39T is just the outstanding value of all the Treasury instruments (T-bills, etc). The entitlement programs (SSA and Medicare) have made commitments to certain levels of service and payments that are far in excess of the revenues they bring in, that's what is meant by "unfunded liabilities".

[margalabargala]

That's not debt, though. Congress can just declare SS/Medicare null and void, or change the amounts, etc. They can't do that with actual Treasury debt.

If you signed up for some expensive monthly subscription, you don't need to do the math about how much it would cost if you keep paying it every month until you die 60 years from now and then freak out about how big that number is. You can just...cancel the subscription.