Trying to export my clip as a Photoshop sequence and the export does not look the same

Hi guys, newbie here. 

I'm following along a tutorial on yt of how to make this cool blur effect. In one of the steps, the creator exports his rotobrushed clip as a photoshop sequence, then imports the sequence so that for one of the steps it's less of a strain on his computer. When I try to do the same, the sequence I end up importing is unalligned with the original clip, and is about a second shorter. Video of the PSD sequence behind my original clip 

Attached: A screenshot of my timeline showing the PSD sequence being a second shorter.

The tutorial I was following: https://www.youtube.com/watch?v=Bhouu0sLNJ0 at 6:54 to about 8:55 is where he talks the photoshop sequence.