TIM doesn't yet support "fill this container 10% with steel plate", but it does understand "fill this container with 500 steel plates", so you'd have to work out the math to see how many items "10%" is. Then, just add a tag to your container like "[TIM SteelPlate:500]" and any time TIM sees that container it will make sure it has 500 steel plates -- that means it will send some if it's short, but it will also take some if it has more than 500.

To make this work, however, you'll also have to remove the DOCK tag (or make it match the station connector's DOCK tag) so that TIM knows it's allowed to process your docked ship in the first place. In order to protect your other containers so TIM doesn't pull things out of them (such as weapon ammo, reactor uranium or oxygen generator ice), you can instead tag those specific containers with "[TIM LOCKED]" and TIM will never remove anything from that container.

Best way is to set a higher priority on a docking ship, to transfer goods from the base or mother ship.

Thanks for the answers, sounds like a great solution.
Is there any limit to how long a tag can be in SE?
Also how do i set priority?

edit - Also how do i combine items, do i use a comma, or a space ro something else?