What does it mean when you have a bracket or two straight lines around a negitive number

When you have a bracket around any number, you need to turn that number into the greatest integer less than or equal to that number. Which means if don't have an integer, round it down to nearest integer.

Ex. [3]=3 [4.87]=4 [8.24]=8

The two straight lines make its inside positive.

Ex. |3.14|=3.14 |-4|=4 |-7/3|=7/3