How do I fix incorrect data?
Update the incorrect point in the Data tab below the graph, then press the Update button.
You can also delete datapoints using the Delete button, though you should do this with extreme caution. Deleting data may trigger an immediate derailment on your graph, if you fall far enough off track after the data is removed.
Note that editing data may not always stick! If your goal uses an automatic data source, Beeminder will likely refetch the original data from the data source and overwrite your changes. It's not that we don't trust you (well, possibly that too) but we need a single ground truth for the data so if the autodata source changes, Beeminder updates the data to match. So change the data at the source then click the button to on the Beeminder goal page to refresh/refetch it. Of course, we also know that sometimes device batteries die and you forget to use them and all of that, so just reply to the legit check if there are extenuating circumstances.
(The weaselproof setting disables datapoint editing and deletion on autodata goals, so it won't even be an option if you've weaselproofed the goal.)