SQL Function - Variable setting itself to random value - function

Question

I have created the below function, and it seems to at random to change the #FCST and #QTY values to random selections. Here is an example of the program in debug returning a bad value for #FCST. As #FCST was at 9.53, I expect it to return 9.53.
CREATE FUNCTION dbo.LTBADJ
(#MAT VARCHAR(30),#LCUT DATE, #QS DATE,#STAT FLOAT, #MCA FLOAT)
RETURNS FLOAT
AS BEGIN
DECLARE #HD DATE
DECLARE #ED DATE
DECLARE #FCST FLOAT
DECLARE #QTY FLOAT
DECLARE #YRS FLOAT
SET #ED =
(SELECT TOP 1 [EO_END_DATE] FROM [dbo].[EO_LTB]
WHERE [W_PART_NUMBER] = #MAT
AND [APPROVED_DATE] <= #LCUT
ORDER BY [EO_END_DATE] DESC)
SET #HD =DATEADD(YEAR,2,#QS)
SET #FCST = (CASE WHEN #MCA <= #STAT THEN #MCA ELSE #STAT END)
SET #FCST = (CASE WHEN #FCST <.5 THEN .5 ELSE #FCST END)
SET #YRS = (DATEDIFF(DAY,#HD,#ED) + 730)/365
SET #QTY = #FCST * #YRS
SET #QTY = (CASE WHEN #ED<=#HD THEN 0 ELSE #QTY END)
RETURN #QTY
END ;
EDIT: Example of #QTY incorrectly calculated

Answer 1

All seems correct - you can see what's going on by running the below SQL.
I suspect the confusion's the e-002 and e-001 on the end of the numbers; that's just SQL trying to display the values of floats; because of how floating point arithmetic works, some numbers are calculated slightly out from what you'd expect, then to try to make them readable SQL will display the numbers with an exponent.
declare #MAT VARCHAR(30) = '50309120000W'
,#LCUT DATE = '2014-10-26'
, #QS DATE = '2014-10-27'
,#STAT FLOAT = 9.5399999999999999e-002
, #MCA FLOAT = 9.5399999999999999e-002
DECLARE #HD DATE
DECLARE #ED DATE
DECLARE #FCST FLOAT
DECLARE #QTY FLOAT
DECLARE #YRS FLOAT
SET #ED =
(
SELECT TOP 1 [EO_END_DATE]
FROM (SELECT '2019-02-28' [EO_END_DATE], #MAT [W_PART_NUMBER], #LCUT [APPROVED_DATE] ) X
WHERE [W_PART_NUMBER] = #MAT
AND [APPROVED_DATE] <= #LCUT
ORDER BY [EO_END_DATE] DESC
)
SET #HD =DATEADD(YEAR,2,#QS)
SET #FCST = (CASE WHEN #MCA <= #STAT THEN #MCA ELSE #STAT END)
SELECT #FCST
SET #FCST = (CASE WHEN #FCST <.5 THEN .5 ELSE #FCST END)
SELECT #FCST
SET #YRS = (DATEDIFF(DAY,#HD,#ED) + 730)/365
SET #QTY = #FCST * #YRS
SELECT #FCST, #YRS, #QTY
SET #QTY = (CASE WHEN #ED<=#HD THEN 0 ELSE #QTY END)
SELECT #QTY, #ED, #HD