Update README.md

README.md

@@ -58,7 +58,7 @@ Each example has the following fields:
 | Field               | Description                                                                                                                  |
 |---------------------|------------------------------------------------------------------------------------------------------------------------------|
 | `contributor`       | Username of the contributor that committed changes                                                                           |
-| `difficulty`        | Difficulty of the problem (assessor-based)                                                                                   |
+| `difficulty`        | Difficulty of the problem (assessor-based. 0 means that fix requires only the code formatting)                                                                                   |
 | `diff`              | Contents of the diff between the failed and the successful commits                                                           |
 | `head_branch`       | Name of the original branch that the commit was pushed at                                                                    |
 | `id`                | Unique ID of the datapoint                                                                                                   |