rsync prints units not conistent. As shown in a typical output like in
* to follow SI prefix standard  and add a single space between the value and the unit:
3.13G -> 3.13 GB
* to note all units in a unique way:
now it is "K bytes/sec" and "kB/s"
* to chose between binary IEC  units and SI units (perhaps ask the user for an option? --iec --si) and wite a short note in the man page like 1 kB = 1000 Byte
or 1 KiB = 1024 B.
* to note "seconds" with the SI symbol "s" 
The user chooses between the 1000 & 1024 units via how many --human-readable options they specify. Rsync uses the same suffixes since it's trying to be brief, and it's left to the reader to know that they represent the units that they requested.