Fiber and pectin and all that doesn't affect the reading at all. I agree with Denny. I just juiced a few of my own apples yesterday and also bought juice from two different places. 1.2 gallons of each times 3 = 3.6 gallons total. Gravities were 1.042, 1.045, and 1.047, for an average of 1.045. This is very normal. When gravity hits about 1.010 then I will add gelatin, rack, and keep cold for unadulterated naturally sweet enjoyment.
Cheers.