I think the repeater rating has to do with duty cycle. In this case I'd guess it means the repeater is capable of (speculating) 90% duty cycle. My other thought is it's got to do with the gain of the antenna or something related to input/output gain. An antenna gain of 9dB would make sense for a repeater.
"Why does the U.S. care which flag will be hoisted on a small piece of land thousands of miles away?" -- Ron Paul