You are correct - the solution for {19, 9, 10, 4', 5, 4, 6, 3, 2'', 1, 4, 1, 3, 2, 4} IS 8,1.
This is one of the example test cases (test.assert_equals(find_incorrect_value([19, 9, 10, 4, 5, 4, 6, 3, 2, 1, 4, 1, 3, 2, 4]),(8,1), "Second node on leaf level should be 1")). So I'm not sure exactly what your question is - I think you understand what is going on!

'This is because of the condition "if the incorrect value occurs on the leaf level, then the right child will always be the incorrect one." Since 9 + 1 != 16, the 1 must be changed to 7, rather than changing the 9 to 15.'