Mention API does not return all mentions



When I use developer API to get the mentions for this user @10456745 (, it’s missing quite a few tweets in there.

If I compare the above results to Advance search for that handler is mentioned, there are more tweets in the advance search E.G.

Also, the mention API doc says it will return 20 results, but I am only getting 15, I am wondering why the missing mentions are not returned by the API? Thanks