Update documentation on job level build variables

doc/ci/variables/README.md

 ## Variables
+
 When receiving a build from GitLab CI, the runner prepares the build environment.
 It starts by setting a list of **predefined variables** (Environment Variables) and a list of **user-defined variables**
 
 The variables can be overwritten. They take precedence over each other in this order:
 1. Secure variables
-1. YAML-defined variables
+1. YAML-defined job-leve variables
+1. YAML-defined global variables
 1. Predefined variables
 
 For example, if you define:
-1. API_TOKEN=SECURE as Secure Variable
-1. API_TOKEN=YAML as YAML-defined variable
+1. `API_TOKEN=SECURE` as Secure Variable
+1. `API_TOKEN=YAML` as YAML-defined variable
 
-The API_TOKEN will take the Secure Variable value: `SECURE`.
+The `API_TOKEN` will take the Secure Variable value: `SECURE`.
 
 ### Predefined variables (Environment Variables)