To view the balances of your current campaigns select | Marketing | Reports | Campaign Account Balances
If you include what is in the current trust balance, the "Vendor Due" figure is the "Vendor Used" less the "Vendor Received"
Or you can choose to exclude what is currently held in trust
The "Vendor Due" figure is "Vendor Used" less amount drawn down "Vendor Received Excluding Trust" leaving the "Vendor Due" amount.
You can also choose to include campaigns with a trust balance, even if the "Vendor Due" is zero.