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.
'91 Pickup - Imelda / '08 Tacoma TRD - Donna
'09 Kawasaki KLR650
'98 Rhygin Juke SS / '12 Gunnar Rockhound 29 / '16 REEB Dikyelous
"Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty. Nobody is able to achieve this completely, but the striving for such achievement is in itself a part of the liberation and a foundation for inner security. " --Albert Einstein