How the bunching is done at stage 6900-7100

I have gone through your website and the fixation of the pay of PGTs of KVS and other central govt. schools.What I did not understand is bunching at three stages at 6900-7100, 7300-7500 and 7700-7900.6900&7700 are bunched and fixed at Rs, 18930 including grade pay.7300&7500 are bunched and fixed at Rs, 19360 including grade pay.7700&7900 are bunched and fixed at Rs, 19800 including grade pay.Where as no bunching is done at 6500 & 6700. Why no bunching in this case? If bunching is done for 6500 & 6700, then the bunching stops at 7700 only. No bunching after the basic of 7700.Can you please clarify on this?Except this difference, I could follow all the fixation tables and in fact they are matching with what I did in case my Teachers.Can you please find answers to the following questions?
1. Why the PRT is fixed at 13500 initially, when pre-revised pay scale of 6500-200-10500 is given to them? (6500X1.86+4200=16290). If not 16290, the pay must be closer to this figure as is the case with all the upgradations.For example: TGT 17140, PGT 18150, Principal & EO 29500.
2. Fitment tables prepared by me, taking the benefit of bunching into consideration gives advantage to the TGTs. Scale of 5500-175 to 7450-225. Whereas the PGT is getting less in his fitment table for scale of 6500-200 to 7500-2503.
3.Don't you feel injustice is done to PRTs in the fitment table proposed.
4. What is the use of giving upgraded scales, when you simply have to multiply the old basic by 1.86 and add the new grade pay? As it hardly gives few hundred rupees benefit.
Seetha Ramaiah Meda
Principal
K V No. 2, Nausenabaugh,
Visakhapatnam-05 (AP)
Please click 'comments' to read/write answers on the published queries.