This slide explains the characteristics of top and bottom contacts and vertical mounts. If the FFC or FPC exposed traces are pointing away from the PCB surface as it enters the connector, then a top contact would be required.  If the FFC or FPC traces are facing towards the PCB as it enters the connector, then a bottom contact would be required. The vertical mount version does not have a top or bottom orientation for the FFC/FPC trace, and the connector itself would be positioned on the PCB in the direction of the conductive traces.