Late Afternoon in the Park

I enjoyed Tai-Chi class at a senior center this morning. Simultaneously, I am studying Tai-Chi movements with DVD which one of my friends gave me. And finally, after four months, I can do the entire movements all by my self now.  However, there was a little problem that There are some different movements  between the DVD and at the class. should I learn two of them as a separate Tai-Chi. It is confusing.