OK, I know it's not quite that simple — debt as a number has political and psychological importance. But I think it helps clear things up to put all of that aside for a bit and focus on the aspect of the situation that isn't a matter of definitions: Greece's primary surplus, the difference between what it takes in via taxes and what it spends on things other than interest. This surplus — which is a flow, not a stock — represents the amount Greece is actually paying, in the form of real resources, to its creditors, as opposed to borrowing funds to pay interest.
Greece has been running a primary surplus since 2013, and according to its agreements with the troika it's supposed to run a surplus of 4.5 percent of GDP for many years to come. What would it mean to relax that target?