Bounces are defined as the number of visits with a single image request (or single hit). Custom links are included, meaning if a visit contains 1 page view and 1 custom link call, it won't be considered a bounce.
So, basically, any visits that have only one hit or one line can be considered as bounces.
You can consider the following columns:
visit_num - tells the visit number
visit_page_num - tell the page number of the visit (filter this column for 1)
page_event - tells the custom link calls - (filter to only include 0 - that is normal page view)
Lookout for visits in the data feed and that should give you Bounces.