Tested in 11G.
1. Need to use minutes.
2. It's all about casting the denominator.
3. Also change the column format to show additional decimal places.
TIMESTAMPDIFF(SQL_TSI_MINUTE, "SF_CS_CS_Fact"."Crtddt_Dt", "SF_Emlmssg_Sum_CS"."Initl Resp Tm") / cast( 60 as real )
TIMESTAMPDIFF(SQL_TSI_MINUTE, "SF_CS_CS_Fact"."Crtddt_Dt", "SF_Emlmssg_Sum_CS"."Initl Resp Tm") / 60.000000000001
(A bit hackish, but easier to tell users sometimes.)
When you specify in the interval in the first argument of TIMESTAMPDIFF you are implicitly telling OBIEE the level of precision that you want. For SQL_TSI_YEAR you are going to get integer values of whole years. if yo uneed to get more granular than that you need to use SQL_TSI_MONTH or WEEK.
Also note, than when performing mathematical operations like divide an multiply, all elements of the calculation need to be a data type that can represent decimal values, or the result of the entire calc will always get converted to an integer.