Alembic ( https://www.curseforge.com/minecraft/mc-mods/alembic ) seems to be slightly incompatible with the Dummy mod, as having both of these mods installed causes the damage values shown on the dummy when attacked are double what they actually are. The actual damage values are unchanged and normal mobs take the damage that they're supposed to take, it's only a visual incompatibility. I've talked to an Alembic dev, and they said the issue can only be solved on dummy's end.