tmm-completion-prompt

tmm-completion-prompt is a variable defined in `tmm.el'.
Its value is

"Press PageUp key to reach this buffer from the minibuffer.\nAlternatively, you can use Up/Down keys (or your History keys) to change\nthe item in the minibuffer, and press RET when you are done, or press the\nmarked letters to pick up your choice.  Type C-g or ESC ESC ESC to cancel.\n"

Documentation:
Help text to insert on the top of the completion buffer.
To save space, you can set this to nil,
in which case the standard introduction text is deleted too.

You can customize this variable.