This morning I weighed the damp pucks after pulling a single and a double on the Delonghi B2C. Results:
Double: 22 grammes
Single: 23 grammes
Allowing a few grammes margin, since the pucks break when they fall into the grounds box and you can't be sure to get it all out cleanly, it's the same quantity of coffee every time, it's just the volume of water that changes. Doubles aren't as sweet as singles, which isn't surprising, but they probably contain proportionately more caffeine.