GMAT Critical Reasoning (CR) | Re: In Patton City, days are categorized as having heavy

This is how I look at answer choice A

1990
fewer days with light rain
fewer days with moderate rain
but 20% more rain

How is this possible?
light rain and moderate rain categories are restricted by range.
That means 20% increase was caused by heavy rainfall (>2).
But we have to find a link which will explain why the difference was just 20% when clearly it rained heavily in 1990.

A clearly does that. It rained heavily in 1990 but on fewer days.

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