represented as greater than is true or reasonable; "an exaggerated opinion of oneself"
If food is overdone, it has been spoiled by being cooked for too long. The meat was overdone and the vegetables disappointing. = overcooked
If you say that something is overdone, you mean that you think it is excessive or exaggerated. In fact, the panic is overdone. As the map shows, the drought has been confined to the south and east of Britain. cooked too much underdone