The number on the right ("cume") is the total number of listeners to each of these stations in a given week:
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That's every radio station in Los Angeles getting a 1.1 or better. KRTH not only has the highest share, it has the highest cume of any station in the market---218,500 more listeners than the second-highest coming station.
It's okay to not like KRTH. It's okay to not understand what KRTH plays, or why it's successful with it. But the fact of the matter is that in its best book of the Drake-Morgan-Steele "golden era", it had a weekly cume of 1,477,710. Today it's 2,321,300.