Undersized Power Adapter Error Message

I have a Precision 7510 updated with the latest Bios and drivers. Today my TB15 arrived. I haven't tested connecting a monitor to it yet only a network cable and USB 3.0 stick - this worked fine.

I also tried starting the laptop from the button on the TB15 which also works fine.

However on startup I receive an error message:

"Alert! You have attached an underasized 130W power adapter to you system, which is less than the recommended 180W power adapter" ... message carries on a bit.

Now the thing is both the TB15 power adapter and 7510 power adapter are the same (identical part number) and  are shown to be 180W output.

What's the problem here and what do I need to do ?