diff --git a/docs/usage/self-hosting.md b/docs/usage/self-hosting.md
index 1f9671349340a2cca9930bd096ab7fc0a7db43e0..e9b33dc91f3565bafd3ff58394a79ff0e9df4797 100644
--- a/docs/usage/self-hosting.md
+++ b/docs/usage/self-hosting.md
@@ -421,3 +421,18 @@ spec:
 
 It's recommended to configure `LOG_LEVEL=debug` and `LOG_FORMAT=json` in environment if you are ingesting/parsing logs into another system.
 Debug logging is usually necessary for any debugging, while JSON format will mean that the output is parseable.
+
+### About the log level numbers
+
+When you use `LOG_LEVEL=debug` and `LOG_FORMAT=json`, Renovate uses numbers in the `level` field.
+
+The logging level output is controlled by the Bunyan logging library.
+
+| Level | Meaning |
+| ----: | ------- |
+|    10 | trace   |
+|    20 | debug   |
+|    30 | info    |
+|    40 | warn    |
+|    50 | error   |
+|    60 | fatal   |