since is what the elapsed-time bound is measured from; every is how many calls one accounting covers (see FlowrGasConfig.countedCheckEvery).
What ended the extraction early, undefined while the budget holds.
Books one processed node, returning whether the budget is used up (so the caller must not descend). Only every FlowrGasConfig.countedCheckEvery-th call does more than count down.
Books one created vertex, sampled like step. Billed as created, so the count bounds the work done rather than the size of the final (possibly merged-away) graph.
Counts what one extraction spends and reports when its DataflowBudget is used up. Both counters are sampled, not exact: the hot paths only decrement a countdown, and accounting runs once every FlowrGasConfig.countedCheckEvery calls, so a bound may be overshot by up to that many steps or vertices.