It is my understanding that Time Machine does not compress as it backs up and that it backs up everything (at least in default mode).
Why then is the space-used stat given by Finder re my external hard drive to which I backed up my iMac's (OS X 10.9.5) internal drive much lower/less than the same stat in re my internal drive from which I backed up. The difference is 354.39 GB on internal vs. 85.83 GB on external.
My first backup took only about 40 minutes, which surprises me - thought would be like 4 hours, so I am wondering if it was complete and successful. However, all the files on my internal do seem to be on the external, and I got not messages indicating that there was a problem. It has been backing up hourly since that initial backup without any problems apparently.
Shouldn't those stats be the same?