org-babel-min-lines-for-block-output

org-babel-min-lines-for-block-output is a variable defined in `ob-core.el'.
Its value is

10

Documentation:
The minimum number of lines for block output.
If number of lines of output is equal to or exceeds this
value, the output is placed in a #+begin_example...#+end_example
block. Otherwise the output is marked as literal by inserting
colons at the starts of the lines. This variable only takes
effect if the :results output option is in effect.