Bounding box in REST API



I am collecting old tweets using REST API by setting bounding box. But most of the time it fails to collect from inside box.
I have set France boundary like this
double lat = 46.2276;
double lon = 2.2137;
double res = 380 ;
String resUnit = “mi”;

Also, it collects from the UK too.
What should I do to get only France tweets?