Results when Limit max rows retrieved in query panel

Hi,

I have a question about the results in a Webi when you limit the rows retrieved.

I limit the query to 300 rows, how the Webi choose the 300 rows from for example 2000 total result of the query. I know that its not the first 300 rows because when i do the query direct in data base with a top 300 the results are different.  

Thanks

Jose