Because of non-functional scale in the organisation and also merger of 5000 & 5500 scale, I need clarification in the following case.

1.Entry Grade appointment on 1986 in the scale of 950/- (GP 1900)
2.First Promotion during 1989 in the scale of 1400/- (GP 4200) as the scale of 1200 not in operation(not in the hierarchy)
3.Second Promotion during 1997 in the scale of 5500/- (GP 4200)
4.Third Promotion during 2007,after completion of 10 years, in the scale of 6500(GP 4600).
In view of merger of scales, actual benefits enjoyed in the scale of 5000, 6500 only. Further, in the above case the employee rendered 18 years in the scale of 5000 (as the scale of 5500 merged with 5000).
Please clarify, his actual entitlement as of now, with a break-up details, please.