Add details for counter metric

Author: lahsivjar

solutions/observability/apps/tail-based-sampling.md

@@ -140,20 +140,28 @@ APM Server produces metrics to monitor the performance and estimate the workload
 
 ### `apm-server.sampling.tail.dynamic_service_groups` [sampling-tail-monitoring-dynamic-service-group-ref]
 
-This metric tracks the number of dynamic services that the tail-based sampler is tracking per policy. Dynamic services are created for tail-based sampling policies that are defined without a `service.name`. 
+This metric tracks the number of dynamic services that the tail-based sampler is tracking per policy. Dynamic services are created for tail-based sampling policies that are defined without a `service.name`.
+
+This is a counter metric so, should be visualized with `counter_rate`.
 
 ### `apm-server.sampling.tail.events.processed` [sampling-tail-monitoring-events-processed-ref]
 
 This metric tracks the total number of events (including both transaction and span) processed by the tail-based sampler.
 
+This is a counter metric so, should be visualized with `counter_rate`.
+
 ### `apm-server.sampling.tail.events.stored` [sampling-tail-monitoring-events-stored-ref]
 
 This metric tracks the total number of events stored by the tail-based sampler in the database. Events are stored when the full trace is not yet available to make the sampling decision. This value is directly proportional to the storage required by the tail-based sampler to function.
 
+This is a counter metric so, should be visualized with `counter_rate`.
+
 ### `apm-server.sampling.tail.events.dropped` [sampling-tail-monitoring-events-dropped-ref]
 
 This metric tracks the total number of events dropped by the tail-based sampler. Only the events that are actually dropped by the tail-based sampler are reported as dropped. Additionally, any events that were stored by the processor but never indexed will not be counted by this metric.
 
+This is a counter metric so, should be visualized with `counter_rate`.
+
 ### `apm-server.sampling.tail.storage.lsm_size` [sampling-tail-monitoring-storage-lsm-size-ref]
 
 This metric tracks the storage size of the log-structured merge trees used by the tail-based sampling database in bytes. Starting in version 9.0.0, this metric is effectively equal to the total storage size used by the database. This is the most crucial metric to track storage requirements for tail-based sampler, especially for big deployments with large distributed traces. Deployments using tail-based sampling extensively should set up alerts and monitoring on this metric.