No need to report this sort of error, each record is transcribed a number of times so errors should be ironed out. 😃
If you notice you made an error before you click on the "next ledger" button, you can correct everything. Just click on the row you want to correct (it will change from red to green), than on the information (i. e. Registration Number) you want to correct, than correct the error and finally click next (or press enter) to store it.
Even after you clicked on "Finish" you can correct anything you want by clicking on "back to transcribing", than correct any errors as I described above.
Only when you click "next ledger" the information will be stored in the database and you can't correct it anymore. But don't worry, everything is transcribed multiple times so errors will be noticed and corrected, as darryluk already wrote.