This opinion can only come from exposure. Whenever I see "one cup" in a recipe I'm 100% baffled. A big cup? A tea cup? One of those larger coffee mugs? Trying to judge what is actually meant here can leads to volumes differing about two to three times in scale.

Give me centiliters, desiliters and liters any day.

I still have no idea what a cup is. And 50-70 ml seems way too little to make sense, so I will just assume you pulled those numbers out of thin air.