Trying to save trimmed quicktime file unsuccessfully

[macbook123]

I would really appreciate if somebody could help me with this crazy problem. I'm trying to save a trimmed quicktime file by exporting to m4a but when I open it the untrimmed full file opens. What am I doing wrong.

 

[macbook123]

I suppose I should also ask if there are any other ways to save than to .m4a? The only way I seem to be able to save trimmed files is through the "Export" feature, but that only allows me one storage format, the .m4a.