FYI: I too have the Anytone AT-778UV and it draws 3.25 amps on low power, 6.0 amps on mid power, and 8.25 amps on high power. I just checked it with my amp clamp.
Amps x Volts = Watts.
So if the voltage is 13.8 and the radio is on high power, the wattage it draws is 13.8 x 8.25 = 113.85 Watts.
So the radio presumably puts out 25 Watts of RF power on high, while DRAWING 113.85 Watts from the power supply.
I tested the range from the radio installed in my vehicle, to my base station, and I got about 6 miles before it started to lose reception. That's using the Browning BR-450 NMO antenna and a discone antenna about 25 feet off the ground for my base station antenna. That was on the highway which had small hills along the way so your results may vary.