DB2 SQL Confusion

I am failing to understand why the following won’t work

SELECT m.index, SUM(d1.amt), SUM(d2.amt)
FROM master m,
detail d1,
detail d2
WHERE m.index = d1.index
AND m.index = d2.index
AND d2.qalif = 1
GROUP BY m.index

I wrote another sql that does work, I just don’t understand why I get higher values on SUM(d2.amt) than I am expecting.

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