luci/applications/luci-app-statistics/root/usr/share/luci/statistics/plugins/rrdtool.json

{
	"title": "RRDTool",
	"category": "output",
	"legend": [
		["DataDir", "StepSize", "HeartBeat", "RRARows", "XFF", "CacheFlush", "CacheTimeout"],
		["RRASingle"],
		["RRATimespans"]
	]
}