mysql group by hour - how to avoid wrong results

In this table the values of my rain counter are stored. The correct total is 0.9 In the RAW Data you can see that at 17:01 the value was set to 1161.5.

By sql query the RAW data are grouped per hour. In the results only 0.6 rain are shown in the time from 16-17 o'clock. Unfortunately the 0.3 mm between counter 1161.5 and 1161.2 are missing.

Any idea how I can avoid the error in my sql query?

• RAW Data from raincounter:

• MYSQL Query:

SELECT `date`,ROUND(MAX(`rainc`) - MIN(`rainc`),2) AS `rain`, MAX(`rainc`) AS max
FROM`mqtt-weather`.`rainc`
WHERE `date` >= CURDATE() AND `date` < CURDATE() + INTERVAL 1 DAY
GROUP BY HOUR(`date`)
    

• Result:

WITH
  lagged AS
(
  SELECT
    r.*,
    LAG(`date`) OVER (ORDER BY unixt) AS prev_date,
    rainc - LAG(rainc) OVER (ORDER BY unixt) AS rainc_delta
  FROM
    `mqtt-weather`.`rainc` AS r
)
SELECT
  MIN(prev_date)     AS interval_start,
  MAX(`date`)        AS interval_end,
  SUM(rainc_delta)   AS interval_rain,
  MAX(rainc)         AS final_rainc
FROM
  lagged
GROUP BY
  unixt DIV 3600

EDIT: added demo and corrected typos and integer division.

Demo: https://dbfiddle.uk/fW1ykZxi