Here are some data samples
Resolved issue. Was simply just a spacing issue with Duration: not properly being aligned.
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Nope. The dur<300 was just a filter I was using. Even if you remove it, no data will still be present.
| where dur < 300
| timechart span=1d avg(dur) as avg_day
dur > 300 on days when there are no graph lines?
dur > 300