Size of file doubled after save ?

[Mike359]

Hi,

Whenever I do a modification of a song, even a small one that reduce the lengh of the song (eg I trim silence at the beginning and end, hence the overall song is say 10s shorter, no other modification), the file size doubles, for example from 3mb to 5mb. At the bottom of the soft, after a file is saved, there is a green mention about higher conversion rate. I don't think I had that originally. 

So my question : did I touch something or is this normal and compulsary ? Is there a setting I could modify (I looked but couldn't find anything) as I don't need extra sound quality whatsoever, I'm happy with the original quality of the song, I mam more into saving space on the hard drive.

Thanks a lot for your help!
Loving your soft :)