rsrt duration information

Hi everybody.

i created a simple query for runtime statics.i am running a query( just company code+ net value)

i looked RSDDSTAT_OLAP table and shows me 1.98 seconds and its true.

but when i running the query via rsrt sum of duration shows me 0.38 seconds and its false..

i noticed that rsrt shows always less for runtime.

why rsrt-disylay statics shows less always?