What do the square brackets mean in $[5-(6-7(2-6)+2)]+4$? While watching a youtube video about a Simpsons math episode at 1:27 there's a puzzle that includes square brackets.
$$[5-(6-7(2-6)+2)]+4$$
Apparently the answer is $-27$ which I can't figure out how to arrive at that answer. I've Googled that the square brackets mean intervals. But then I don't understand the context of this question as surely an interval should be two numbers separated by a comma?
How do you arrive at $-27$?

$$[5-(6-7(-4)+2)]+4 \implies [5-(6+28+2)] + 4 \implies [5-36] +4 \implies -27$$
