The default highest-resolution retention period for graphite is 10 seconds, but it is configurable in graphite.
If you emit a metric from this fluent-plugin-graphite any faster than every 10 seconds, multiple values for the same metric may reach Graphite at any given 10-second timespan, and only the last value would take hold and be persisted - so your data would immediately be partially lost.
To fix that, simply ensure your flush interval is at least as long as the highest-resolution retention.
See more here