When Science has no Benchmark

"Academic Excellence." 
"Research Excellence."

"Assess the publication activity of the candidate relative to your expectations of someone with their academic experience."

I still have no idea what exactly these mean. Even objective measures, like grades, are rarely objective. For example, Prof#1 might consider an average of 95 as impressive, while Prof#2 might consider an average of 85 as impressive.

How are trainees, who sometimes later become full-fledged scientists who get academic careers, supposed to gauge their progress relative to their peers? True, we have mentors, but as mentioned, different faculty consider different level of work as excellent.

But I guess that's life, eh? There is rarely a benchmark and we just make do. But recognising that doesn't make my training any easier or more clarifying.

It is frustrating.