I've just had new windows installed.?

I've just had new uPVC windows installed on my house. We went for the equal sight line options which means that on the non-opening window it has a dummy window so they look the same size just that it won't open. In the bottom left hand corner is wobbles a bit and I was wondering if this could mean the window will fall out. Or how is the dummy window fixed into the frame (it looks like its pushed in from the outside so how would they secure it?)