Hi 1357rabbitlover.
This is an interesting subject, and one that will have many rabbit owners debating on for probably years to come. If you think about it logically, rabbits in the wild do not have pellets to eat. They get the fiber they need from grasses, vegetables and the odd bit of fruit - whatever they can find, in effect.
There is a growing trend to not include pellets in a pet rabbits diet at all, and to just feed excellent quality hay, along with vegetables to round out the diet. The reason we use pellets is mainly for convenience, and to ensure that our bunnies get the correct nutritional value in their diet.
The problem is that there are wildly varying qualities of rabbit pellets, and some have ingredients that are simply in there to keep the cost to the buyer down and the profits to the manufacturer up (not all pellets, I hasten to add).
It comes down to a matter of common sense. If you're feeding pellets as part of your rabbit's diet then you should of course take the manufacturer's guide lines into account. Then you need to assess your rabbits on a regular basis to check that they're at the correct weight.
As a very broad generalization, if you're feeding pellets then adult rabbits should have timothy hay based ones, and approx 1/2 a cup per day, per 6lbs of rabbit. Of course, this is a very general rule and needs to be tweaked for each individual case.
Hope that helps a little.
Cheers,
Small Pet Select