How to use EntityFieldQuery to get number of certain product referenced from line items purchased on a certain date range?

Hi

I've been fiddling around with EFQ to get Commerce related data.

I've got following code which produces result '11' but I've got no idea what it represents:

 $reserved = new EntityFieldQuery();
 $reserved
        ->entityCondition('entity_type', 'commerce_line_item', '=')
        ->count();

It should count the number of line items? Included in orders and "active" carts?
Shop has only one order(cart) with 3 products so I can't tell what is this 11.

If I modify it as follows it returns 7:

 $reserved = new EntityFieldQuery();
 $reserved
        ->entityCondition('entity_type', 'commerce_line_item', '=')
        ->fieldCondition('commerce_product','product_id','2','=')
        ->count();

And how could I check which fields and properties are available for line item?
I know how I've customized them and