deduct 60 minutes/ 1 hour from punch time (Start time) of attendance
Something like this? If you share your table structure the answer could be more precise.

-- TEST TABLE
CREATE TABLE dbo.employees(id int identity(1,1), 
                           StartTime datetime2);

-- TEST VALUE
INSERT INTO dbo.employees (StartTime)
VALUES(getdate());

--CHECK
SELECT * FROM dbo.employees;

-- ACTUAL UPDATE
UPDATE dbo.employees
SET StartTime = DATEADD(hour,-1,StartTime);

-- CHECK AFTER UPDATE
SELECT * FROM dbo.employees;