One interesting thing about T-SQL (the flavor or SQL that comes with Microsoft SQL Server), is that the RAND() function to seed a random number is called once per query. You can work around this using user defined functions, OR, just use the NEWID() function.

NEWID creates a GUID, but can be cast into a whole manner of different data types. I like this:

DECLARE @maxval TINYINT, @minval TINYINT
select @maxval=24,@minval=5

update tbl_orders set quantity=CAST(((@maxval + 1) - @minval) *
    RAND(CHECKSUM(NEWID())) + @minval AS TINYINT)
    where abs(quantity)>24