Question

Why does the summary need to be revised?

Answer 1

Um, which summary?
If you're talking about this;
Read the summary of the section of "The Beginnings of the Maasai," where the volcanic eruption and its results are described.

As a result of a volcanic eruption, Enkai and the cattle were thrown into the sky. Enkai wanted to save his cattle. He grew a tree that bridged the sky and the earth. The cattle walked down the tree to Neiterkob. Neiterkob and the Maasai tribe took over caring for the cattle.

Why does the summary need to be revised?

Then the answer is:
The summary lacks transitions that connect ideas