A Signed Long Integer is a 32 bit signed integer in 2's complement form.
It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive).
For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else.
This data type will most likely be large enough for the numbers a program will use.
If a wider range of values is needed use long instead.