Fish feeding confusion

So i have been getting ready for my first tank and one issue I am still very unclear on is that of feeding. I have read all over the place "feed as much as they will eat in X amount of time" my issue with that nothing is ever said about quantity or rate of feeding. I would feel more comfortable with something along the lines of a measurement or at least how many pellets/sec or something. Or at least someone tell me how long a common size package of food lasts, such as hikari cichlid excel or NLS 1mm pellets.

-Kevin