The data collected for some of your histograms have not been used recently. If these histograms are no longer needed, they should be removed.
Histograms and the percentage of total space used:
This.is.a.histogram (-1TB, -0.000000%)

Note from the Chrome Metrics team:
This bug was created and assigned to you because your histograms have not been viewed in the last 90 days. If the histograms are no longer needed, please remove them to help us and Chrome users save resources. If some of these histograms will be used, you can remove the unused histograms and mark this bug as "Fixed". We'll remind you again in a few months if the remaining histograms are still unused. If you would like to use this histogram to monitor for outliers, subscribe to it on Chirp (https://uma.googleplex.com/chirp) and it will count as being used.

If you think there was an error, let us know at chrome-metrics-team@google.com.