I think i am incorrect about this; but here it goes anyways..
On a number line, there is negatives and positives. As such, if there's only negatives, you must start with the lower negative due that it is much more huger than the bottom negatives.
Now then, if there's positive and negatives on there, go for the positive. The negatives are lower than positives, and it'll always stay like that.
But! If it doesn't make any sense, take a look at this.
5-, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5.
See the pattern? -5 is the lowest one out of all them, due that the negatives that are currently raising, it is going into the positives. So you must add the greater number first.