Your documentation page http://dev.datasift.com/docs/getting-started/data/twitter contains sample output for a retweet. What would a retweet of a retweet look like? Or a retweet of a retweet of a retweet? Are such constructions even possible?
Retweeting a Retweet appears in the same way as Retweeting an original Tweet. There are only two constructions of a Tweet you can receive through DataSift - an original Tweet, or a Retweet.
So if A tweets something which is then retweeted by B we get a datasift data item that reflects this fact. But when C then receives the retweet from B and then retweets again, do we get a datasift data item that tells us that C has retweeted something from B or from A?
This depends to an extent on the way the Tweet is Retweeted.
If @User_B Retweets @User_A's Tweet "properly" (by clicking a Retweet button), when @User_C comes to Retweet @User_B's Retweet, @User_A will be attirbuted with creating the original Tweet.
If @User_B Retweets @User_A's Tweet by copying the Tweet, and prefixing the Tweet with "RT @User_A: ........", this is not technically a proper Retweet, so @User_B will be attributed with creating the Tweet if @User_C Retweets it.