Which Nanda was indicated by the Saptarishis in Purvashaada Nakshatram : Vishnu Puranam

References :

Apparent Conflict :

Wilson assumed that both shlokas 104 and 112 of the 4th Amsa, 24th Adhyaya of Vishnu Puranam refered to the same Nanda. (Maha Padma Nanda) This conflicted with totals from the 23rd Adhyaya.
While Shloka 104 (Parikshit to Nanda – 1050 years – Vishnu Puranam ) mentions 1050 years – the totals in 23rd Adhyaya give (See : Magadha from Jarasandha to Satavahanas as per Vishnu Puranam) :

Others have assumed that Saptarishis in Purvashaada Nakshatram refers to the same Nanda. This creates even a bigger problem, because the only way to get 1050 years from Maghaa to Purvashaada is to count forwards, whereas Kaliyuga Raja Vrttantam tells clearly that we should count backwards. Counting back wards give us 1650 years. For Details See : Saptarishi (Great Bear) Positions according to Varahamihira and Vateswara

Resolution :

The shorter duration of 1050 years refers to the Nanda of the Pradyotana dynasty
The longer duration of 1500 or 1650 years refers to MahaPadma Nanda (whose children were replaced by Chanakya). That is why the phrase Nandat Prabhrutyah in sholka 112.

Discrepancy between 1500 and 1650 years :

The period of Sahadeva, the son of Jarasandha was at least partly in Dwapara Yuga
Vatesvara also gave a correction for the duration of Saptarishis indicating each Nakshatram from 100, as given by Varahamihira and Vrddha Garga to 94 years 6 months and 20 days. (See : Vatesvara, an ancient Kashmiri Astronomer, his Karanasara and Siddhanta : R.N. Rai, INSA ) This explains a difference of 90 years (approx) in the total.
Assuming that there must be some more small correction figures, arrived at by later astronomers, we can take the figure of 1500 years between Parikshit and Mahapadma Nanda as quite accurate.

Ancient Indians – Satya Samhita