.. option:: offset=int
- Start I/O at the given offset in the file. The data before the given offset
- will not be touched. This effectively caps the file size at `real_size -
- offset`. Can be combined with :option:`size` to constrain the start and
- end range that I/O will be done within.
+ Start I/O at the provided offset in the file, given as either a fixed size or
+ a percentage. If a percentage is given, the next ``blockalign``-ed offset
+ will be used. Data before the given offset will not be touched. This
+ effectively caps the file size at `real_size - offset`. Can be combined with
+ :option:`size` to constrain the start and end range of the I/O workload.
.. option:: offset_increment=int