Sources:

Ken Smales - The First 125 Years

Review
According to a letter in the Nottingham Journal on 10 Nov 1888, Forest scored 7 goals in this game:

'Evidently it is desirable that football matches should commence earlier, as it is almost impossible for some of the spectators to ascertain whether goals have been scored towards the conclusion, owing the advance of darkness A mistake was made in the match between Forest and Mitchel St Georges a fortnight ago, and last week at Hereford a similar error was made. The Reds scored seven times, not six as reported. I see that the Notts match commenced earlier today.'