You can simply click on "Edit", delete the details shown (making sure you provide a reason statement) and replace with your own inputs, again making sure you show a reason statement, as well as providing sources as back-up.
However, at the same time you should send an internal message to the person who recorded the erroneous detail, explaining why you made your changes and offering to collaborate with them in working on the individual / family in question in this Family Tree branch. You may not receive a response, but at least you will have tried to reach out to them in line with the Family Tree ethos.
Thank you Paul... I will work on making the corrections, and will explain reason for change.