W3C - Cargo Shuttle movements

There are now many cargo shuttle in flight.
most of them are moving products to Tiny Atlas.

Not sure if everyone is up to date on how these shuttles go about transports.

when a transport is started, up to 20 cargo shuttles you own, must pick up the products you want to move.
The products are stored on a space center.
you might have cargo shuttles parked at that space center.
in that case, these will be used for the transport.

If there are no cargo shuttles available at the space center where products should be picked up, cargo shuttles you own, in other locations, will be called upon to move to the space center and pick up the products.

This may cause many empty cargo shuttles to move between space centers while you did not explicitly asked for.

The cargo shuttles will then move from the place where they were parked, to the space center where they need to pick up products and then move from there to their destination.

The shuttles will deliver the products at the destination.
if more needs to be moved, they will start a next round.
once a cargo shuttle delivers the products and there are no more products to be moved, it will stay where it is and wait for a next transport request.

it's not always the case. i set up some cargo transfers, many times and although i had shuttles parked, empty ones from other space station started to move. for me is not a big issue, as they move around, i always get shuttles parked everywhere in the end.
the problem i encounter is another one. i own about 1500 cargo shuttles, set up wind turbines transfer, 36 transfer orders with 20 wind turbines each but only one or two cargo shuttles went executing the orders. i even get an exclamation point asking if i have enough shuttles available.
if 20 shuttles execute the order, at 36 transfers i should get 720 shuttles moving in order to get thing moving faster.

how do they work actually? i could't find any info except this post so far

i found what the issue was. all my cargo shuttles had the order to move, but they didn't.