Both the B757 flight crew and their Dispatcher misinterpreted the minimum amount of fuel required in the affected tank when dispatched with the Aft Boost Pump inoperative.

Narrative

I was just notified of an inadvertent error in interpretation of a Maintenance Carry Over (MCO) item - an inoperative Right Aft Boost pump - by our Dispatcher; which we failed to catch as well. We were not 'rushed' during our preflight and took the time to thoroughly review the item. My copilot read the MEL line for line. Our only question was the minimum fuel value statement under the procedures section. Since it stated 'minimum fuel value' of 12;200 LBS and not specifically [individual] 'tank value' we did not challenge our dispatch fuel of 17;000 LBS for our short 50 minute flight. The Dispatcher also read the requirement to be total versus tank value. In hindsight; I should have called the Dispatcher to make sure that we were both on the 'same page' with the MEL interpretation.I consider myself a very meticulous Captain who asks questions and is not afraid to call for assistance when needed. However; in this case I was incorrect in my assumption that the flight plan was correct. In reviewing the situation; my First Officer and I believe the MEL should be updated with more specific wording. In the future I will be more vigilant and ask more questions of Dispatchers and Maintenance; especially when fuel totals are involved.I believe the MEL should be rewritten so that there is 'no doubt' about how much fuel should be on board. I was surprised to read the 767-300 procedures clearly stated what the minimum value was for takeoff and landing for the 'affected tank'. The 757 procedures simply stated 'minimum fuel values' next to these numbers. Had the 757 MEL mirrored the 767-300; I believe we would have caught the Dispatcher's error. In addition; I recommend that MEL also state the required minimum total fuel on board. Finally; the MEL should state the 'total unusable fuel' value of 3;000 LBS as well.