SQL Server 2019

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CREATE TABLE #x
(
  RecordId int, 
  RecordDateTime datetime, 
  AttributeA char(6), 
  AttributeB char(6), 
  Amount DECIMAL(12,2), 
  [Value] int
);

INSERT #x(RecordId, RecordDateTime, AttributeA, AttributeB, Amount, [Value])
VALUES
  (1,  '2020-08-01 00:00:00', 'AttA01', 'AttB01', 10.00,   6510),
  (2,  '2020-08-01 00:00:00', 'AttA01', 'AttB01', 11.00,   3620),
  (3,  '2020-08-01 00:07:00', 'AttA01', 'AttB01', 17.00,  87430),
  (4,  '2020-08-01 00:15:00', 'AttA01', 'AttB01', 15.00,   4140),
  (5,  '2020-08-01 00:20:00', 'AttA02', 'AttB01', 30.00,   2350),
  (6,  '2020-08-01 00:30:00', 'AttA01', 'AttB01', 20.00,  14560),
  (7,  '2020-08-01 00:46:00', 'AttA01', 'AttB01', 15.00,   1370),
  (8,  '2020-08-01 02:15:00', 'AttA01', 'AttB01', 30.00,   1380),
  (9,  '2020-08-01 02:30:00', 'AttA01', 'AttB01',  5.00,   4490),
  (10, '2020-08-01 02:30:00', 'AttA01', 'AttB01',  6.00,  13100);
  
  
 ;WITH x(a,b,d,am,v,is_anchor) AS 
(
  SELECT AttributeA, AttributeB, RecordDateTime, Amount, [Value],
      CASE WHEN DATEDIFF(MINUTE, COALESCE(LAG(RecordDateTime, 1) 
      OVER 
      (
        PARTITION BY AttributeA, AttributeB ORDER BY RecordDateTime
      ), '20000101'), RecordDateTime) > 15 THEN 1 ELSE 0 END
  FROM #x
),
y AS 
(
  SELECT *, 
    grp = SUM(is_anchor) OVER 
          (PARTITION BY a,b ORDER BY d ROWS UNBOUNDED PRECEDING)
  FROM x
),
z AS 
(
    SELECT d, a, b, is_anchor,
      Amount = SUM(am) OVER (PARTITION BY a,b,grp), 
      StartValue = FIRST_VALUE(v) OVER 
                   (PARTITION BY a,b,grp ORDER BY d, v),
      EndValue = FIRST_VALUE(v) OVER 
                   (PARTITION BY a,b,grp ORDER BY d DESC, v DESC)
    FROM y
)
SELECT RecordDateTime = d, AttributeA = a, AttributeB = b,
       Amount, StartValue, EndValue
FROM z
WHERE is_anchor = 1
ORDER BY d, a, b;

RecordDateTime	AttributeA	AttributeB	Amount	StartValue	EndValue
2020-08-01 00:00:00.000	AttA01	AttB01	73.00	3620	14560
2020-08-01 00:20:00.000	AttA02	AttB01	30.00	2350	2350
2020-08-01 00:46:00.000	AttA01	AttB01	15.00	1370	1370
2020-08-01 02:15:00.000	AttA01	AttB01	41.00	1380	13100