Cubase 6 Artist Pack - Audio Mixdown Problem

Well, I have a problem with Audio Mixdown, I’m using Cubase 6.03 Artist Pack. The file size of the .wav file can get upt to 78mb and won’t go lower than 64mb.

I don’t know why and the song is only 3 minutes and 7 seconds. I’m only using vocals and a beat (the beat is around 1.5mb alone)

Please help me, I really need it. It’s appreciated.

What samplerate and bitdepth are you using to export?