Exporting as csv and Feed API help

Ultimately I would like to get data with a specific to and from time using the API. Looking at the API help page http://emoncms.org/feed/api

it states http://emoncms.org/feed/data?id=1?start=0&end=0&dp=100

1. What is dp? When I use it it only ever gives me the first data entry for that feed (Pic1)

2. No matter what values I use for start and end it always gives me the whole list of values (Pic2)

 

Help much appreciated