Should be `start_in` not `start_key`

doc/ci/yaml/README.md

@@ -681,7 +681,7 @@ Delayed job are for executing scripts after a certain period.
 This is useful if you want to avoid jobs entering `pending` state immediately.
 
 You can set the period with `start_in` key. The value of `start_in` key is an elapsed time in seconds, unless a unit is
-provided. `start_key` must be less than or equal to one hour. Examples of valid values include:
+provided. `start_in` key must be less than or equal to one hour. Examples of valid values include:
 
 - `10 seconds`
 - `30 minutes`