Guided Project: CIA Factbook SQL query output wrong


(A)
I am trying to get the birth rate as a sum of total births then add up the top 5 to see top5 as a fraction of the sum of total births using CTE but it does not add up correctly please advise?

Total of top5 comes in at
fraction (%)
0.008752164214835342

which does not match total from second photo 0.0103 + 0.0102+0.009 etc

(B)
could the difference between these two queries be explained please I know the output is different but do not understand why? I do not understand why the first one returns a constant value.

   %%sql
    SELECT name,(SELECT birth_rate/SUM(birth_rate) FROM facts)AS b
    FROM facts
    ORDER BY b DESC
    limit 5

    SELECT name,birth_rate/ (SELECT SUM(birth_rate) FROM facts) fraction
     FROM facts
     ORDER BY 2 DESC
     LIMIT 5