docs: clarify blocked_evals metrics (#13751)

Related to #13740

- blocked_evals.total_blocked is the number of evals blocked for *any*
  reason
- blocked_evals.total_quota_limit is the number of evals blocked by
  quota limits, but critically: their resources are *not* counted in the
  cpu/memory

website/content/docs/operations/metrics-reference.mdx

@@ -258,9 +258,9 @@ those listed in [Key Metrics](#key-metrics) above.
 | `nomad.nomad.blocked_evals.memory`                   | Amount of memory requested by blocked evals                                    | Integer              | Gauge   | datacenter, host, node_class                            |
 | `nomad.nomad.blocked_evals.job.cpu`                  | Amount of CPU shares requested by blocked evals of a job                       | Integer              | Gauge   | host, job, namespace                                    |
 | `nomad.nomad.blocked_evals.job.memory`               | Amount of memory requested by blocked evals of a job                           | Integer              | Gauge   | host, job, namespace                                    |
-| `nomad.nomad.blocked_evals.total_blocked`            | Count of evals in the blocked state                                            | Integer              | Gauge   | host                                                    |
+| `nomad.nomad.blocked_evals.total_blocked`            | Count of evals in the blocked state for any reason (cluster resource exhaustion or quota limtis) | Integer | Gauge | host |
 | `nomad.nomad.blocked_evals.total_escaped`            | Count of evals that have escaped computed node classes. This indicates a scheduler optimization was skipped and is not usually a source of concern. | Integer | Gauge | host |
-| `nomad.nomad.blocked_evals.total_quota_limit`        | Count of blocked evals due to quota limits                                     | Integer              | Gauge   | host                                                    |
+| `nomad.nomad.blocked_evals.total_quota_limit`        | Count of blocked evals due to quota limits (the resources for these jobs are *not* counted in other blocked_evals metrics) | Integer | Gauge | host |
 | `nomad.nomad.broker.batch_ready`                     | Count of batch evals ready to be scheduled                                     | Integer              | Gauge   | host                                                    |
 | `nomad.nomad.broker.batch_unacked`                   | Count of unacknowledged batch evals                                            | Integer              | Gauge   | host                                                    |
 | `nomad.nomad.broker.eval_waiting`                    | Time elapsed with evaluation waiting to be enqueued                            | Nanoseconds          | Gauge   | eval_id, job, namespace                                 |