Actual data consumption much larger than movie size listed on iTune when streaming

Hi all

I rented a movie through iTunes on HD which I saw was roughly 4.5GB and chose to stream it using my mobile/cellular data on my iPhone using the TV app as I couldn't download the movie without connecting to WiFi.

I started streaming after midnight today and went to bed immediately after and therefore would not have used bandwidth today beyond streaming the movie. After waking up, I checked my usage for today and it was nearly 8GB! Before I call my mobile provider to inquire I figured I might check here.

The only thing I could think of which may have contributed to this is that I have used the slider bar on quite a few occasions through the movie to jump back to an earlier point in the movie for a minute or so each time to spot if I missed something before jumping back to the original point. As far as I can remember, the jumps were not instantaneous (unlike saved videos).

My theory is that when streaming, I am downloading the video faster than I am viewing it so as the prevent interruption, however I assume as streamed data isn't cached on the iPhone whenever I jump back and forth, the pre-downloaded part of video is gone and the video would just re-download again in advance each time I jump resulting in a much larger data consumption than the original video size.

If the above is correct, then if I stream the movie from start to finish without jumping, would this mean the data usage would be as stated on the iTune description?

Thanks in advance.