Not a lot of results with scoring TRUE

Enabling the scoring "Freshness vs. Quality" I get a maximum of 4/5 results and selecting 12 hours sometimes show more results than 24. How is this possible?
Is there something to know or to tune up to make the getItems function showing a good amount of tweets?

My database is populated correctly and the .pid is working as per "ps aux | grep fetch".
Am I missing something?
