Need offset to push subtitles forward

I need to push all my subtitles forward about 3 seconds but the offset values I
enter only seem to push them backwards. If I enter an offset of
00;00;03;00 then the subtitles start three seconds earlier and I want them to
start 3 seconds later.

I've tried entering a - before the value but it won't take that and I've tried
entering 23;59;57;00 and that puts them clear off the map somewhere in la la
land. My show is 22 minutes long and it has hundreds of Spanish subtitles so I
don't what to have to change every in and out time. I just want to offset the
whole group forward relative to the video and I can't figure out how to
accomplish that.

Help would be much appreciated.