It appears the racing record of Bonny Black has been confused by the GSB and Pick with races run by two other horses of the Duke of Rutland, [Old] Ebony (1714) and the Duke of Rutland's [Basto] Mare (1715), with some of the races of these two mares erroneously being attributed to Bonny Black. Adjusting for this, the likely true racing record of [Old] Ebony is as follows:-

2 Oct 1718 - 50gns match Newmarket v Mr Frampton's Woodstock (Hunter); 9 Aug 1719 - 100gns Hambleton (beating 31 others)

9 Oct 1719 - 2nd Noblemen's Contribution Money Newmarket; 9 Apr 1720 - 2nd King's Plate [mares] Newmarket (to Whitefoot)

Grandam of Plaistow (1737 King's Plate Newmarket, 1739 King's Plate The Curragh); the GSB makes her dam of Plaistow but 18th century stallion adverts in the Dublin Journal show that Plaistow is out of a daughter of Old Ebony by Sutton's Grey Arabian

For research on her racing record by A.J. Hibbard see:-

https://www.bloodlines.net/TB/Bios2/Bios-B/BonnyBlack.htm