chore: added example of criteria AND in SLO (keptn/keptn/#6106)

service_level_objective.md

@@ -91,9 +91,23 @@ objectives:
   key_sli: true
 ```
 
-Further assume, that in the previous evaluation error_rate was 5%. The upper limit for pass is 5.5% (5 + 10%). The following list shows the evaluation results for all possible error_rate values.
-*   pass: <= 5.5%
-*   fail: > 5.5%
+Further assume, that in the previous evaluation the metric response_time_p95 was 5. The upper limit for pass is 5.5 (5 + 10%). The evaluation results for all possible values would be:
+*   pass: <= 5.5
+*   fail: > 5.5
+
+Listed criteria are combined using a logical OR, so if we consider the pass criteria in our example it is enough either for  "<=+10%" to be satisfied or "<600".
+To enforce multiple criteria at the same time (logical AND) it is enough to list them in the same criteria element, for instance the following would enforce for response time not to be higher than 10% compared to the previous value nor to be greater than 600:
+
+```yaml
+objectives:
+- sli: response_time_p95
+  displayName: "Response Time P95"
+  pass:
+  - criteria:
+    - "<=+10%,<600"
+  weight: 2
+  key_sli: true
+```
 
 ## Scoring