This process worked for me to ninja-delete a specific days worth of data due to a haywire sensor.
Just a nutshell for anyone who might want to take an easier route and simply delete all the energy data of a specific day, this query will work:
DELETE
FROM "statistics"
WHERE "created" like '2021-09-16%'
Of course change the date itself, but leave the % symbol, as it is the wildcard (since the timestamp is always different).
You can delete only a specific sensor instead of a whole day by more closely following the post linked above.