Clarify search max depth variable

doc/user/application_security/sast/index.md

@@ -412,7 +412,7 @@ Some analyzers make it possible to filter out vulnerabilities under a given thre
 | Environment variable          | Default value            | Description                                                                                                                                                                                                                 |
 |-------------------------------|--------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | `SAST_EXCLUDED_PATHS`         | `spec, test, tests, tmp` | Exclude vulnerabilities from output based on the paths. This is a comma-separated list of patterns. Patterns can be globs, or file or folder paths (for example, `doc,spec` ). Parent directories also match patterns. |
-| `SEARCH_MAX_DEPTH`            | 4                        | Maximum number of directories traversed when searching for source code files. |
+| `SEARCH_MAX_DEPTH`            | 4                        | SAST searches the repository to detect the programming languages used, and selects the matching analyzers. Set the value of `SEARCH_MAX_DEPTH` to specify how many directory levels the search phase should span. After the analyzers have been selected, the _entire_ repository is analyzed. |
 | `SAST_BANDIT_EXCLUDED_PATHS`  |                          | Comma-separated list of paths to exclude from scan. Uses Python's [`fnmatch` syntax](https://docs.python.org/2/library/fnmatch.html); For example: `'*/tests/*, */venv/*'`                                                  |
 | `SAST_BRAKEMAN_LEVEL`         | 1                        | Ignore Brakeman vulnerabilities under given confidence level. Integer, 1=Low 3=High.                                                                                                                                        |
 | `SAST_FLAWFINDER_LEVEL`       | 1                        | Ignore Flawfinder vulnerabilities under given risk level. Integer, 0=No risk, 5=High risk.                                                                                                                                  |