Help in processing calculation with hhmmss

Assume you have a table contains 3 values you supplied and a id column as key, like this

	[id] int identity(1, 1),
	[Processed_%] float,
	[processed_on] datetime,
	[processed_in_hhmmss] varchar(20)

To resolve the requirement, can use following steps:

1. Split the processed_in_hhmmss value to hours, minutes and seconds. The value in this column must be formated well as HH:mm:ss.
2. Calculate how many seconds have been spent, it equals hours * 3600 + minutes * 60 + seconds.
3. Calculate how many seconds will be spent to finish the process.
4. Calculate the expect date and time then output them.

Full dode:

CREATE TABLE #test
(
	[id] int identity(1, 1),
	[Processed_%] float,
	[processed_on] datetime,
	[processed_in_hhmmss] varchar(20)
)

INSERT INTO #test
([Processed_%], [processed_on], [processed_in_hhmmss])
VALUES (0.08, '2025-01-28 15:55:17', '4:8:40')

GO

WITH C1(id, o, v)--Get hours, minutes and seconds that have spent, the rows o=1 contain hours, o=2 contain minutes, o=3 contain second 
AS
(
	SELECT t.id,  b.ordinal, b.value FROM #test t
	CROSS APPLY string_split(t.processed_in_hhmmss, ':', 1)b
)
,
C2(id, expected_datetime)--Calculate
AS
(
	SELECT t.id,  DATEADD(second, (ss.second_spent / t.[Processed_%]) * (1 - t.[Processed_%]), t.[processed_on]) expected_datetime FROM #test t --Calculate the expected_datetime 
	INNER JOIN
	(
		SELECT id, SUM( CASE o WHEN 1 THEN v*3600 WHEN 2 THEN v*60 ELSE v END) second_spent --convert spent time to seconds 
		FROM C1 
		GROUP BY id
	)ss
	ON t.id = ss.id
)
SELECT t.*, --output results
	CAST(C2.expected_datetime AS TIME) Expected_finished_in_hhmmss,  
	C2.expected_datetime Expected_Date FROM #test t INNER JOIN C2
ON t.id = C2.id

DROP TABLE IF EXISTS #test

That's really to less on information.
Please post table design as DDL, some sample data as DML statement and the expected result.