I have to say that the order of two substrings with the same length is so unclear.
I failed in the test only because of the order.
There must be much more explaination about it.

In a case of having "2 11", I'd prefer the output to be sorted by stable sort, but it's your choice.

Good idea, I did it.

I also corrected the random test which always returned True.

I have explained that idea in the description - while the forth smallest value is -9, you may sum all the values in the array that are between -9 to 39 (included). Because you have two more values of -9 the sum is 58 and not 76.

I'd write in the description "In this Kata you are given two vectors and you should compute 'Manhattan distance' " or something similar to this.

I had to change the name of the function from "distance" to "manhattan_distance", otherwise the tests didn't work.