Controversial Horoscope Interpretation (I hope someone can explain)?

Even in India there are different systems of calculation followed by different schools, e.g., Sayana and nirayana syatems. Then there are different almanacs followed which do not show identical position of planets and stars. Even for the predictions, there are different schools of thought. In identical combinations and positions of stars and planets reading as per Parashara, Vrigu and Jaimini are not same always and in all respect. The controversies, if any, are sorted out by studying the events of the past thoroughly and meticulously.