add test comment

Signed-off-by: Haoyang Li <[email protected]>

integration_tests/src/main/python/date_time_test.py

@@ -574,8 +574,10 @@ def test_timestamp_seconds_long_overflow():
         conf={},
         error_message='long overflow')
 
-# Make sure every decimal value in test data is 'Rounding necessary' by set full_precision=True to
-# avoid leading and trailing zeros
+# For Decimal(20, 7) case, the data is both 'Overflow' and 'Rounding necessary', this case is to verify
+# that 'Rounding necessary' check is before 'Overflow' check. So we should make sure that every decimal 
+# value in test data is 'Rounding necessary' by setting full_precision=True to avoid leading and trailing zeros.
+# Otherwise, the test data will bypass the 'Rounding necessary' check and throw an 'Overflow' error.
 @pytest.mark.xfail(condition = is_not_utc(), reason = 'xfail non-UTC time zone tests because of https://github.com/NVIDIA/spark-rapids/issues/9653')
 @pytest.mark.parametrize('data_gen', [DecimalGen(7, 7, full_precision=True), DecimalGen(20, 7, full_precision=True)], ids=idfn)
 def test_timestamp_seconds_rounding_necessary(data_gen):