.count metric naming convention only applies to UpDownCounters

CHANGELOG.md

@@ -80,3 +80,6 @@ release.
   ([#70](https://github.com/open-telemetry/semantic-conventions/pull/70))
 - Clarify that OTEL_SEMCONV_STABILITY_OPT_IN is a comma-separated list of values
   ([#104](https://github.com/open-telemetry/semantic-conventions/pull/104))
+- Update `.count` metric naming convention so that it only applies to UpDownCounters,
+  and add that `.total` should not be used by either Counters or UpDownCounters
+  ([#999](https://github.com/open-telemetry/opentelemetry-specification/pull/999))

specification/metrics/semantic_conventions/README.md

@@ -13,7 +13,8 @@ linkTitle: Semantic Conventions
   * [Name Reuse Prohibition](#name-reuse-prohibition)
   * [Units](#units)
   * [Pluralization](#pluralization)
-    + [Use `count` Instead of Pluralization](#use-count-instead-of-pluralization)
+    + [Use `count` Instead of Pluralization for UpDownCounters](#use-count-instead-of-pluralization-for-updowncounters)
+    + [Do not use `total`](#do-not-use-total)
 - [General Metric Semantic Conventions](#general-metric-semantic-conventions)
   * [Instrument Naming](#instrument-naming)
   * [Instrument Units](#instrument-units)
@@ -114,7 +115,7 @@ should not be pluralized, even if many data points are recorded.
 * `system.paging.faults`, `system.disk.operations`, and `system.network.packets`
 should be pluralized, even if only a single data point is recorded.
 
-#### Use `count` Instead of Pluralization
+#### Use `count` Instead of Pluralization for UpDownCounters
 
 If the value being recorded represents the count of concepts signified
 by the namespace then the metric should be named `count` (within its namespace).
@@ -125,6 +126,20 @@ to the processes then to represent the count of the processes we can have a metr
 `system.processes.count`. The suffix `count` here indicates that it is the count of
 `system.processes`.
 
+This rule SHOULD only be applied to UpDownCounters, since (monotonic) Counters have
+`_total` appended to their names when they are [mapped to Prometheus](../../compatibility/prometheus_and_openmetrics.md#otlp-metric-points-to-prometheus), which would lead to
+`_count_total`.
+
+#### Do not use `total`
+
+Counters SHOULD NOT append `_total`  to their names. Counters have `_total` appended to their names when they are [mapped to Prometheus](../../compatibility/prometheus_and_openmetrics.md#otlp-metric-points-to-prometheus),
+which would lead to `_total_total`. The reason that the Prometheus mapping cannot
+suppress adding the duplicate `_total` is because then the mapping wouldn't be
+bidirectional.
+
+UpDownCounters SHOULD NOT use `_total` either because then they will look like
+monotonic sums in Prometheus.
+
 ## General Metric Semantic Conventions
 
 **Status**: [Mixed][DocumentStatus]