reftex-cite-view-format

reftex-cite-view-format is a variable defined in `reftex-vars.el'.
Its value is

"%2a %y, %T, %B, %j %v:%P, %s %<"

Documentation:
Citation format used to display citation info in the message area.
Must NOT contain %l. See the variable `reftex-cite-format' for
possible percent escapes.

You can customize this variable.