TrimFromStart

public float TrimFromStart { get; set; }

[C#]
using (Presentation pres = new Presentation())
{
    ISlide slide = pres.Slides[0];
    IVideo video = pres.Videos.AddVideo(File.ReadAllBytes("video.mp4"));
    var videoFrame = slide.Shapes.AddVideoFrame(0, 0, 100, 100, video);

    //set triming start time 1sec
    videoFrame.TrimFromStart = 1000f;

    //set triming end time 2sec
    videoFrame.TrimFromEnd = 2000f;
}