since you only want to see the first 3 records in the detail section (i'm presuming), go to the section expert and for the detail section next to the suppress, click the 'x-2' button. In the you will need to find the running total that you created...same name as listed under the running totals. Double click the running total, and after is type > 3. Click OK all the way back to the report. This will hide (suppress) all entries where the running total is greater than 3. Don't forget to have a reset on your running total or you will only see 3 records for the whole report.
Hope this helps.