Help me understand OpenWeatherMap rain data

So I am using this integration: OpenWeatherMap - Home Assistant (free plan, Mode: hourly, language: en)

It clearly says this:

rain - Rain volume for the last hour, mm.

However, since I’ve worked a lot with time series data, this does not make any sense to me. This is definitely not Rain volume for the last hour:

So long story short - it seems that data is returning rain interval every 5 minutes. Sudden drop in rain volume seems like it’s showing not of the past hour, but of the past 5 minutes?

I’ve found several threads on this forum regarding topics, like how to get rain volume of past day, but it seems I am the only one with this strange data representation. Sudden falls in volume does not correlate with hourly rain volume. :confused:

How does this data work?

It’s essentially a rolling total from the last hour; here’s a discussion about it:

I don’t use that integration, but I agree, it seems like a rather useless sensor (and poorly labeled and documented).