I  purchased Movie Studio 16, and having a problem in file size.

I found the files size after editing becomes huge when exporting.
Is it because of the grade of software I purchased? (i.e. Is it because it is not higher grade, such as Platinum?)
Or, is it just because I could not find a proper option?

The case I experienced is as follows:
 - Original file size : 18MB for 8 mins
 - File size after simply removing latter half : 200MB for 4mins.

Of course, the file size becomes small if I select lower quality option.
However, such movie's quality is far away from acceptable level.  As far as I tested, to keep the similar quality as before, file size becomes very huge compared with the original.
In addition, I could reduce the file size to 1/10 by using online service.

What I would like you to tell me is not "which option is best". 
I  just want to know "the reason why file size becomes huge is because the software grade is low" or not.

Best regards,