This means a config file for one of my mods that takes a list of blocks + probabilities is set up incorrectly, such that the probabilities added up exceed 1. Unfortunately the log message is bad (sorry lol) so I don't know which mod it is. It's not really a big deal though, and I think it may even be a bug due to a rounding error.

I only have Integrated API + Integrated Dungeons & Structures installed