To limit query rows, select Limit number of rows to on the Query Builder -Fields page and enter the desired number of rows.
For example, if your company has a large customer base and you want a report on the first 100 customers to which your company made a sale, you would select Limit number of rows to and enter 100 as the desired number of rows. (This assumes that you sort your report by customer.)
Using this example, you could also create a report on the last 100 customers by sorting by customer and changing the sort order. See Sorting Data for information on how to change the order in which the data is sorted.