Twitter4j, confused by the number of tweets returned for a search query



I’m using twitter4j to search tweets with a query string and below is the code that does this:

Query query = new Query( queryStr );
query.setCount( 100 );
QueryResult result = query );
List tweets = result.getTweets();

I issued two queries: Q1 = “twitter text research” and Q2 = “twitter research” and it returned 100 and 65 results for the two queries respectively. Since all the results for Q1 valid for Q2 (since search results are identified by keyword matching) why the number of hits for Q2 is only 65 (or how can this be lesser than 100?)? What’s happening here?