Welcome to the Seven Forums! MLavore
That would be about right for the small amount of drive space your main installation uses. The image compresses data into an archive. This is why you will see that smaller in size.
Once you start adding more programs, files, etc. you will notice the size of any newer image growing in size as well. For 375gb in taken on a 1tb drive here the latest image was seen at 320gb. It would have been smaller then that but some files are not able to compressed as much as others.
(video and certain other file types mainly)