Forget abut comparing your animal to other I have 8 months old animals that are 500/600 grams and this means nothing. What is the most IMPORTANT is that your BP look healthy.

There is no chart for ideal weight, it depends on various factor the animal itself, weight out of the egg, how fast the animal was started, prey size, feeding frequency, food refusal (some will eat no matter what, some will skip) etc.

The breeder was up front regarding assisting and this is something else to account for (smaller prey less often in the beginning), not something I would be very worried about, all the holdbacks that I had to assist turned out to be some of my best feeders (I have one right ow sitting at a 1000 grams at 1 year).

Now the only thing is the prey size YOU are offering rat or mice fuzzies are too small at that size your BP can take an adult mice or a small rat pup.

Again weight is a number overall look and proportion is what matters.