When you add files into queue, StrongDC++ puts them immediately into search queue. It means that search request is sent to hub in intervals you have set for your favorite hub (or global settings when 0). For example, if you add 30 files into your queue and your search interval is set to default (i.e. 10 seconds), then 30 search requests will be sent to hub with 10 second delay between each one.
When you add files into queue, StrongDC++ puts them immediately into search queue. It means that search request is sent to hub in intervals you have set for your favorite hub (or global settings when 0). For example, if you add 30 files into your queue and your search interval is set to default (i.e. 10 seconds), then 30 search requests will be sent to hub with 10 second delay between each one.