Question on instruction for adding additional powerline adapers.

I have a current Poweline Ethernet network with the AV200 and the XAV1004.  I want to add two additional adapters, and have purchased the PL1010 adapters.

In reading in the instructions for adding adapters to an existing network, after installing the first new adapter, I read this:

   "If you want to add additional Powerline adapters, press the Security button on the next adapter for 2 seconds, and then press the Security button on any additional adapters in your network for 2 seconds. The adapters retain security settings even if they are unplugged."

  I am confused about the wording with the "next adapter."  Should that be the security button on any of the adapters on the current network, or the new one I just added?