When I zoom in on your station (unfortunately I cannot zoom in to the highest level) the graph seems at least to make sense of you look at the rate during the first hour of rain, it almost matches the accumulated rain. Our is calculated at the server, I guess there is a mistake in the rate when zooming out. It still doesn’t explain the difference with your other measurements. You might want to measure the old fashioned way.
Take some high glass, wait for rain. After the rain is gone, measure the amount of water, and multiply that by the ratio between the surface area of the opening of your glass and one square meter.
edit: see comment above or Change in graphing rain rate