https://github.com/mraof/Minestuck/blob/fd80e52a3abc490bd3fed8012cb0e3437a73b88b/src/main/java/com/mraof/minestuck/entity/ai/attack/AttackByDistanceGoal.java#L147 Says Mth. instead of Math. ?

line 155 also says Mth, idk if it was a typo or not, i'm just looking through the code for the imp ai that stops aggro at the certain echeladder tier

That's not a typo, it refers to minecrafts class Mth. Likely named as such as it serves a similar purpose to javas Math class, but where they overlap, Mth is sacrificing accuracy for performance.
Had it been an actual typo so that it didn't match any class or the wrong class, the code wouldn't compile in the first place.