minor fixes

docs/sources/features/datasources/prometheus.md

@@ -76,7 +76,11 @@ Name | Description
 For details of *metric names*, *label names* and *label values* are please refer to the [Prometheus documentation](http://prometheus.io/docs/concepts/data_model/#metric-names-and-labels).
 
 
-It is possible to use some global template variables in Prometheus query template variables; `$__interval`, `$__interval_ms`, `$__range` and `$__range_ms`, where `$__range` is the dashboard's current time range and `$__range_ms` is the current range in milliseconds.
+#### Using interval and range variables
+
+> Support for `$__range` and `$__range_ms` only available from Grafana v5.3
+
+It's possible to use some global template variables in Prometheus query template variables; `$__interval`, `$__interval_ms`, `$__range` and `$__range_ms`, where `$__range` is the dashboard's current time range and `$__range_ms` is the current range in milliseconds.
 
 ### Using variables in queries
 

docs/sources/reference/templating.md

@@ -274,6 +274,9 @@ The `$__timeFilter` is used in the MySQL data source.
 This variable is only available in the Singlestat panel and can be used in the prefix or suffix fields on the Options tab. The variable will be replaced with the series name or alias.
 
 ### The $__range Variable
+
+> Only available in Grafana v5.3+
+
 Currently only supported for Prometheus data sources. This variable represents the range for the current dashboard. It is calculated by `to - from`. It has a millisecond representation called `$__range_ms`.
 
 ## Repeating Panels