this is from the RT Users Guide.
–summary [format-string] - Show a listing-style summary of the tickets
found. format-string is used to display particular information about a
ticket. It is made up of object specifiers whose format is %
object may be one of:
width sets the column width of each object. Thus %subject20 will display the
first 20 characters of the subject line. If format string is ommitted, rt
will use the environment variable $RT_SUMMARY_FORMAT if it is set, or an
internal default. The default as of RT version 2.0.9 is:
RT also inserts two blank spaces between each column.