With the twitter API you can only get up to 200 posts per page. You would have to add a &page=x to get the page of tweets (there is a hard limit of 3200 posts)
View the api documentation here
https://dev.twitter.com/docs/api/1/get/statuses/user_timeline
An example of the api call for json would be
https://api.twitter.com/1/statuses/user_timeline.json?include_entities=true&include_rts=true&screen_name=twitterapi&count=200&page=2
and an example for the xml call would be
https://api.twitter.com/1/statuses/user_timeline.json?include_entities=true&include_rts=true&screen_name=twitterapi&count=200&page=2
So what i would suggest is if you want to get all 3200 posts is to set up the script in a function to change the page number each time