Let's take a representative example.

I won't do all your homework for you, but this will be a fun example to work through.

Luke 24, his last chapter, relies on at least 4 eyewitnesses, but likely dozens more.

It begins with Mary Magdalene's personal account of finding the empty tomb. Joanna and the other Mary are also mentioned by name, and could be potential eyewitnesses as well, but the Magdalene takes center stage, making the account most likely hers.

Peter adds in a few brief lines after her account.

The third eyewitness is Cleopas, one of the two disciples on the road to Emmaus, recounting his encounter with Jesus in detail.

The fourth eyewitness is at least one of the Eleven, who passed on Jesus' appearance to them.

This is a minimum of four separate accounts, yet the events were witnessed by so many that dozens and dozens more eyewitnesses could have been consulted and corroborated. (Especially considering the Ascension, the likely event with 500+ eyewitnesses, is included). Because of this, we can't say exactly how many the high number is, but we can say that at least 4 eyewitnesses contributed here, and that just for one chapter.

Luke takes care to delineate when the perspective shifts, making it fairly easy to identify separate accounts. It'd be fascinating to parse out the whole Gospel this way.