Hey hows everyone going ?

I have a strumming question .

I am learning the beginners version of Runaway Train and I am confused .

So the strumming pattern is DD UU DU .

So when do I change chords i,e most chords in this song are 2 bars and when I slow the vid lesson down it would appear to me most 2 bar chords seem to be changed after the folowing DD UU DU DD UU DU ie 2 x DD UU DU ???

Can somebody please explain is this correct

Cheers Dave