It is a very common forecast in the US to have “50% chance of rain on Tuesday” for example. For NWS, they are clear that this is the probability of rain anywhere in the forecast area times the expected percentage of area affected.
In my experience, we almost never get inches of rain forecast unless it is noteworthy, e.g. 4 inches of rain, or it is wintery precipitation like snow or sleet.
This is what those in the US are used to getting in the forecast. So seeing 0.1 inches of rain is just as hard to understand for us, or maybe just me, because it isn’t part of our normal weather experience.