If the video is too early, add extra 00's to the command, like this:
That will start it halfway through the measure
That will start it 1/4 through the measure
etc, just play around with it
If it's starting too late, that's a little trickier. The easiest way to do this would be to add this command:
which, in this case, will make the first measure last twice as long as normal.
This is fine if there's no other notes in the first measure, however, if there are notes in the first measure, you'll have to pad every command in the measure with extra 00's at the beginning for everything to sync up.
This is pretty easy if you're doubling the first measure like the above example, in which case you just double the notes in the first measure by padding each command with 00's at the beginning. Otherwise you'll have to do some math and/or play with it to get it to sync up, which can be a huge pain in the ass if the video starts at a weird time.