SQL Problem Updating A Column Of Type DECIMAL(11,4)

This problem is strictly an SQL problem, and I am about to lose my mind over it.  I have a table named Inventory that has a column named PartialQty which is of type DECIMAL(11,4).  I have shortened my query for simplicity, but here it is.

DECLARE @pqty1  DECIMAL(11,4)

SELECT @pqty1 = PartialQty FROM Inventory WHERE InventoryID = @invIDPRINT @pqty1 UPDATE Inventory   SET PartialQty = 6.5513   WHERE InventoryID = @invID

SELECT @pqty1 = PartialQty FROM Inventory WHERE InventoryID = @invIDPRINT @pqty1

Before this query is ran, the value in PartialQty is 1.2345.  If I run this 2 times in a row, this is the output I get:

RUN 1:

1.2345

(1 row(s) affected)

(1 row(s) affected)

(1 row(s) affected)

(1 row(s) affected)

6.0000

 

RUN 2:

6.0000

(1 row(s) affected)

6.5513

 

I don't understand 2 things.  One is why the first run displays (1 row(s) affected) 4 times even though there is only one record with that InventoryID.

And the other thing I don't understand is why the first time I run it, it loses all of the values after the decimal point. 

Please help,

Scott