Gpx sync when video started later than activity

Hi All, I'm pretty new to Virb but already was able to create several cool videos with it.
Currently I have a problem with syncing the video with gpx data as my camera started recording a couple of seconds AFTER I started my FR 910xt.
What I need to do is in G-Metrix Sync option to keep the Step 1 at time 0:00 and at Step 2 to set to -2 seconds (Or in Activity Start Time to set the same negative value). Is this possible, am I missing an obvious thing here?

Thanks!