Windows

The first number is the file size and the second number is the reference to the number of bytes used on the disk in a particular cluster,it will grow by association with hidden files for example.

You don't really see 2 different sizes for your files or folders. 173KB is equal to 177,152 bytes. What is shown is the size of the file in two different units.
1KB is equal to 1024 bytes (ie. if you divide 177,152 by 1024 you would get 173)
It's the same as saying the length of a stick is 12 inches or 1 foot.

Jeff

The first number represents the actual total bytes these files are in size. The second number represents the actual total bytes plus the slack space (or total bytes of all clusters used). Slack space is space at the end of each cluster that's not used.

Your HD is organized into a certain number of clusters times the cluster size. The number of clusters and cluster size is based on HD size and file type used (FAT, FAT32, NTFS, etc). DOS/Windows allocate space for files using whole clusters. Example: if you have a 6 gig hard drive, and use Win98 with FAT32, your cluster size is 4096. When you save a 323 byte file, the OS will allocate one whole cluster to store it. The actual space used is only 323 out of 4096. The rest of the space in that cluster is wasted and called slack space. That slack space is not usable by another file.

As noted, this difference represents "slack space" at the end of the last cluster. Average "waste" space on a disk is # of files times 1/2 cluster size. Your example suggests you're using 32K clusters. You might want to consider changing to FAT32 and regaining a LOT of disk space...