This section describes what In-file delta technology is and how it can be used to reduce size of backup
[Block Size] defines the size of block used when detecting changes between last full or delta file and the file to be backed up. In general: In-file delta backup with small block size:
In-file delta backup with large block size:
For most cases, the default setting [Auto] will select the optimal block size for each file (depending on the size of the file).