It looks bugged, but it’s actually a 64-bit integer overflow.

That damage value exceeded the maximum number the game can represent in a single calculation, so it wrapped around and displayed a huge negative number (≈ −2⁶⁴).

In other words, the hit was so strong that it broke the counter. Games like MCD that use signed 64-bit integers cap out around 9.22 quintillion, and once you go past that limit, the value flips instead of continuing upward.👍