Ed, they mean the ACC terminal that you hooked to. They are asking for a wire that is hot when the ignition is turned on and you found one. It's just that it is also hot when you turn the key to the ACC position and want to listen to the radio. If you would like a HOT only while the ignition is on, you will have to tap into one of the ignition switch wires that is hot in the ON position and OFF in the ACC position. Use a test light to find one.
If you are worried about the current draw of you guages on that switch terminal, use a relay with an in-line fuse to supply your guages and have the ignition wire switch the relay on. Let me know if you need a diagram.
Rob