Question, 600ex-rt, off camera, manual mode

Hi guys

Trying to learn off camera flash technique, and have a question about manual, off camera settings.

600ex-rt, off camera mounted in a PCB umbrella softbox. I have the flash set to
INDIVIDUAL SLAVE in accordance with the manual. It is fired optically by the pop up flash on my 70d.

Now, here is a page from the 70d manual

IMAGE LINK: http://www.flickr.com …01292417@N03/11​246960945/
image by dynalmadman, on Flickr

Manual says, 'The manual flash output setting will be applied to all external Speedlites.'

The bottom line addresses flash output. Here is my question (finally!)

Does this mean I can set the flash output power of the 600ex from the camera? Or do I have to set the power output on the flash and tell the camera what power I have it set to?

It would be great to change it from the camera, as the softbox setup makes it impossible to change the flash settings when installed. Gotta pull the flash out of the box to access the settings.

Hope this question is clear, I appreciate your time
Michael