Double coil means that your program has more than one rung that turns an output address on or off. That won't work the way you expect it because of the way a PLC operates.
A PLC evaluates each rung of logic in sequence and keeps track of the on/off status of the the outputs. Once it has reached the last rung of the program it sends the on/off status of the outputs to the actual output devices. It does not send the status to the actual outputs immediately after evaluating the rung. Then it reads the status of the physical input devices and repeats the evaluation of the ladder logic rungs, sends the results to the output devices, reads the inputs, evaluates the logic, and so on until you tell it to stop.
So, the signal the PLC sends to the physical output device will be based on the last rung the PLC evaluated before it sends the status to the devices. If you only have one rung that turns the output on or off, the output device will behave as you expect. If you have two different rungs turning the output on or off you'll get surprises.
For example, if rung 10 says turn the output on and rung 20 says turn it off, the actual device will be off. Conversely, if rung 10 says turn the output off and rung 20 says turn it on, the actual device will be on.