The one I did about two years ago took me three hours to complete. I'm not sure if we're talking about the same store, though, as the estimated time to complete was two to three hours for my assignment (I think).
I remember having to take two photos each of the store's left and right-side wall displays. The guidelines stated that the first photo should be taken from the beginning to the middle of the left wall, and the second from the middle to the end of the left wall. Then, I had to do the same for the wall on the right. There was no way to fit all of that in two photos: the floor displays were so close to each other and to the wall that I could not move back to get the required amount of the wall in the frame. I ended up taking three photos, thinking that my report would be rejected. It surprisingly wasn't.
Another frustrating thing was the process of uploading the photos. They wanted me to name them a certain way, which I found out after having uploaded them all with my own labels. So, it took me a long time to delete everything and start all over.
All in all, it was a new experience for me and I was a new shopper, so everything was going slower than I anticipated. I must have spent five-six hours on the assignment in total, which resulted in a poor hourly wage.