Can you explain to me what's a sample for this mod? what does 100000 max samples mean in the config? For example, it says taht it succeded in a radius of 10000 blocks with 151 samples but I don't understand what that means.

A "sample" refers to when a chunk is checked to see if it contains the structure the compass is searching for. If it does, the search succeeds, otherwise, the next chunk is sampled. maxSamples in the config refers to the maximum number of these checks that can be performed in a single search before the search is killed. This and maxRadius are used to ensure a search cannot continue infinitely.