Ok! I see here that that warning might be a phpMyAdmin bug but nothing related to your issue.
Can you execute this SQL command to get your databases size?
SELECT table_schema "Schema_Name", Round(Sum(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" FROM information_schema.tables GROUP BY table_schema;
Can you also execute this other command to check the size of your
du -h /opt/bitnami/mysql/