Yup, I agree. Your project length (as may be viewed in the Transport, where the length is displayed in bars) is probably what you bounced. So you know, Logic doesn't automatically bounce a file according to the length of recorded material. You have to manually set the start and end of your bounce, and that's done by using the method that Rounik described -- setting the cycle length to reflect the start and end of your bounce.
Another way of putting this is: setting the L and R locators to reflect the length of your bounce, and then turning Cycle on. And there are many ways of setting the L and R locators, including the key command that sets the L/R locators to reflect the length of a selected region(s).
Finally, you don't have to re-bounce your part to reduce the file length. Lay up the bounce on a new audio track. Then trim that region in the arrange area. Next, open the sample editor and use the trim function and your file will be permanently ("destructively") shortened to the length of the region. Before you commit, though, make sure that you listen carefully to the start and end of the recording to be sure you're not going to truncate the beginning/end with this operation.