List - Packed

This represents the compressed size of data in a ShrinkIt archive.  The size does not include archive overhead (e.g. storage of the filename, CRCs, and file attributes).

On a disk archive, this indicates the size needed to store the file.  Some files take less space than you might expect because they are "sparse".  On filesystems that support sparse files (ProDOS, and to some extent DOS 3.3), a block filled entirely with zeros isn't actually stored on the disk.  Instead, the file system structure is updated to indicate that there is a gap, and when the file is read the missing data is filled in with zero bytes.