The optional extentSize argument of the fileAttributes command enables you to specify the number of bytes that you require for the growth increment extent of database files; for example, explicitly (16384) or by using a prefix multiplier (16K).
The default value is 64K and the minimum value is 4K.
You can specify both this argument and the initSize argument (separated by a space), the extentSize argument only, or the initSize argument only.