ما الخطا فى هذا الكود

السلام عليكم ورحمته الله وبركاته

ما الخا فى هذا الstored حيث انه يظهر الخطا التالى ولا ادارى ما سببه

ALTER PROCEDURE [dbo].[insertamount11]
	-- Add the parameters for the stored procedure here
@emp_id int,
@start datetime,
@price decimal (7,3),
@end datetime,
@num int,
@mony decimal (5,3),
@name1 int 
AS
BEGIN

	SET NOCOUNT ON;
DECLARE @S Int

	INSERT INTO amount1 VALUES (@emp_id,@start, @price, @end, @num, @mony, @name1) 
SET @S = (SELECT dbo.amount1.num FROM dbo.amount1 WHERE emp_id = @emp_id AND start = @start)

WHILE @S > 0
BEGIN

	INSERT INTO childamount VALUES (@emp_id,@mony,dateadd(mm,1,@start))
	SET @S = @S - 1
	end
END

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.