Merge pull request #3945 from newrelic/retention-updates

fix(data retention): added more detail to the metric rollup info.

src/content/docs/telemetry-data-platform/manage-data/manage-data-retention.mdx

@@ -533,11 +533,13 @@ Your retention changes take effect within 24 hours after updating.
 
 ## Metric data rollup
 
-[Metric timeslice data](/docs/using-new-relic/data/understand-data/new-relic-data-types#timeslice-data) is generated by APM (both custom metrics and default metrics), mobile, and browser agents. Metric timeslice data is aggregated like this:
-* first to 1-minute rollups retained for 8 days
-* then aggregated to 1-hour roll-ups for 90 days
+[Metric timeslice data](/docs/using-new-relic/data/understand-data/new-relic-data-types#timeslice-data) is generated by APM (both custom metrics and default metrics), mobile, and browser agents. A metric timeslice consists of three parts: a metric name, the segment of time the metric represents (the "timeslice"), and a numeric value (the measurement). APM, broswer, and mobile agents can collect thousands of metric timeslices per minute for a variety of performance metrics, such as error rate, bandwidth usage, and garbage collection time. 
 
-Key metric data is stored indefinitely. We meter on the size of the initial 1-minute rollup, not on any of the subsequent rollups. Read on to learn the key metrics by product.
+Metric timeslice data is aggregated and rolled up:
+* first to 1-minute increments, known as rollups, that are retained for 8 days
+* then, after 8 days, those 1-minute rollups are aggregated to 1-hour roll-ups that are retained for 90 days
+
+Key metric data is stored indefinitely. We meter on the size of the initial 1-minute rollup, and not on any of the subsequent rollups. Read on to learn the key metrics by product.
 
 ### Key metrics reported by APM, browser, and mobile