The various RTL8187-based wifi adapters I have are rated 300mw, 500mw, 1000mw, 1500mw, etc, on their product packaging. Are they all correct or are all of them lying? What's the real (or normal) power-rating of a wifi adapter based on the RTL8187 chip?
As far as I know, the chip itself does not determine the power of a WiFi adapter. The chip only produces a signal which is then amplified and broadcast by a transmitter. It is this transmitter which determines the adapter's power.
So what you read is perfectly normal.