If you are using Superstore data then it's normal behaviour, because of it's aggregation of original data. It does it row level, not on agg table level. So it's normal thing
i am not getting you.
please explain below line in details
It does it row level, not on agg table level. So it's normal thing
Do you see an aggregation around the calculation.
It is probably returning sum of DATEDIFF("day",[Order Date] ,Today() ) for the level of detail in your sheet. e.g. if you have State as the only dimension in your sheet, this will compute DATEDIFF.. for each row in your table then sum them up within each state. So if you have 10 transactions in State X it will calculate DATEDIFF for each transaction then sum those up. If you don't want to see it per row item, you can turn off aggregations from analysis menu or in your sheet use a dimension that uniquely identifies each row.