Unknown number of picks at a location/warehouse

We run a number of large warehouses and processes 20k+ orders a day.

We would like to use Dear to order route and split orders between locations, which it can/does do. 

However, in planning and forcasting the work at each warehouse for the day, we are unable to see the numbet of picks allocated to a location? 

Through the API you can get that an order is allocated to a location, however the actual picks are not necessarily from that location and may differ. 

We would like to use the API to fetch orders, together with the line items, and their respective pick locations – this does not seem to be available in the API?