When someone says, "please don't exaggerate," they are asking you not to overstate or embellish the truth or the facts. Exaggeration involves magnifying or overstating something beyond what is accurate or reasonable. It can be done intentionally to make a point more dramatic or to emphasize a certain aspect of a story or situation.
By asking you not to exaggerate, the person is likely expressing a desire for honest and accurate information or a sincere discussion without any added hyperbole. They may feel that exaggeration can lead to misunderstandings or misrepresentations of the facts and may want to ensure that the conversation remains grounded in reality and truth. It's a request to communicate in a more straightforward and measured manner.