The syntax that is in the image is in Backus–Naur form for the et_datatype_spec clause. The syntax is as follows:

et_datatype_spec ::=
{
[UNSIGNED] INTEGER [EXTERNAL] [(len)] [delim_spec]                          
|{ DECIMAL | ZONED } [EXTERNAL] [(len)] [delim_spec] (precision [ , scale])
|ORACLE_DATE                                                    
|ORACLE_NUMBER [COUNTED]                                      
|FLOAT [EXTERNAL] [(len)] [delim_spec]
|DOUBLE
|BINARY_FLOAT [EXTERNAL] [(len)] [delim_spec]
|BINARY_DOUBLE                          
|RAW [(len)]                                                
|CHAR [(len)] [delim_spec] [trim_spec] [date_format_spec]      
|{ VARCHAR | VARRAW | VARCHARC | VARRAWC } ([length_of_length ,] max_len)
}