Default [Q] Real Racing 3 asset download.

I have downloaded Real Racing 3 game on my Asus Zenfone 4.
I downloaded the 42MB app from playstore. After launching the game it asked to download 3245MB of more data. While it was being downloaded the progress showed only 99MB had been downloaded whereas in Data Usage I saw that the actual data that the RR3 had downloaded using WIFi was nearly 1.1GB.
Why is such a huge difference between the two. Also I observed that the data was getting downloaded at a very slow speed. It took hours for it to download just 325MB OF THE DATA. Whereas when I download any data(movie or software)it downloads 400MB in less than a Hour at around 80KBps.
Can anyone solve this mystery?