How to interpret precipitation probability? Below is the Dallas precipitation forecast I just got (requested from Google
at 10am, Nov 29, 2019).

From this, what is the probability that a 10cm (diameter) cup placed in a
Dallas park from 4:00pm will have some visible water in it at 4:10pm?

What about at 4:20pm?

I have never understood what the 61% in the chart really is forecasting
and really want to know the probability of my getting hit by a liter of
rain in a random 20 minute run...just asking two simpler questions here to
work my way up.
Given only this information and nothing else, there isn't really a definitively correct answer.

In reality, it depends on the nature of the precipitation. 61% could mean that there is a 61 percent chance of a thunderstorm between 4 and 5 PM, but since thunderstorms are short-lived, it might only be raining for 10 out of 60 minutes.

61% could also mean that an area of precipitation has a 61% chance of passing over Dallas. If that's the case, then it might be a 61% chance of rain for the entirety of the hour and a 39% chance of no rain at all.