There are five levels in dashaa systems like Vimshottari &c. What is the implication of the names of these dashaa sub-periods ?
The finest level is called "Praana-dashaa". Next is Sookshma. In Vedic Philosophy, the third level should be called "Sthoola" , becasuse starting from the finest level of "Praana", we move to sokhma shareera and then to Sthoola shareera. But the Sthoola level is called Pratyanara.
The implication is that the Sthoola (crude) fruit of Vimshottari must include MD (Mahaa dashaa), AD (Antar Dashaa) and PD (Pratyantara Dashaa). No fruit should be deduced from MD alone, or AD alone, or even with MD + AD. The crudest fruit comes from MD + AD + PD. This is the meaning implied in the nomenclature of dashaa levels. It means MAJORITY of dashaa levels decide the final outcome. MAjority among five levels is three. Hence, PD computation must be perfect for using these Dashaa systems.
Suppose you have to face an interview for selection into some job and you want to predict on the basis of Vimshottari dashaa system. All five levels of Vimshottari cannot be similar, some of them may yield positive result, some may be negative, while some may be mixed. It is the majority type which wins. If the majority verdict is positive, then you will be selected in the interview. For this majority, at least three out of five levels must support the outcome. Hence, three levels make up the minimum requirement for Sthoola prediction. Four is Sookhma, and Five is Praana. Praana is the finest level of existence of the Praanee in this world, hence there cannot be any sixth level.
But some internet gurus have invented a sixth level called "Deha dashaa". They have full right to experiment with new ideas, but it is wrong to go against Vedic philosophy in the name of Vedic Jyotisha. Sooksma and Praana is followed by Atmaaa (Soul) and not by Deha, but pure Atmaa has nothing to do with worldly happenings. Deha is not finer than Praana. Hence the nomenclature "Deha" is conceptually faulty, and speaks about the materialist Dehavaadi attitude of such astrologers who think Deha is the ultimate state, finer than Praana.
Next point is even more significant. Unless DAC (Dashaa Onset Chakra) is used, you must use all three charts of Sudarshana Chakra (SC), namely LK (Lagna Kundali), SK (Surya Kundali) and CK (Chandra Kundali) for ascertaining the outcome. Suppose the MD is of Jupiter and you have to predict the fruits due in Jupiter's MD. For it, you have to find out functional beneficence / maleficence of Jupiter. Suppose it is 1L + 4L (lord of lagna and 4H) in LK and seated in 9H, which makes it highly auspicious. But in SK it is 3L + 6L and seated in 11H, which makes it highly inauspicious. In CK, it is 8L + 11L and seated in 3H, which makes it highly inauspicious. When we combine the fruits of LK, SK and CK, insuspiciousness surpasses auspiciousness, hence the MD will be malefic. But judging from LK alone, the astrologer will predict a highly benefic MD.
Thirdly,relevant divisiona charts and VPC (Varsha Pravesha Charts) also play their roles, and often suppress the Vimshottari results of birthchart. For instance, if D1 has Jupiter's MD which is malefic for career which is our opic, but the MD planet of D10 (which may be some other planet) is benefic in D10 at that time. D10 has a lower Vimshopaka strength than D1, but if Jupiter in D1 is weak by dint of sitting in enemy's sign, but the MD planet is exalted in D10. Then, D10 will suppres the results of D1 almost completely, and the SC result of D10 should prevail according to the Vimshottari sequence deduced from the Lunar longitude in D10. Same with VPC : if VPC's Jupiter is exalted and birthchart's Jupiter is weak, then during MD of Jupiter, VPC will suppress the outcome of birthchart during that year.
These nuances of Vedic Astrology are almost always ignored by astrologers, which gives them wrong results, and instead of following the correct methodology based on classics, they start inventing new ideas, thinking that the rules of classics no longer work ! There are some astrologers who have no time to test the ideas laid down in classics and are more interested in novelties of modern era in the name of "progress".