How do i split a stack of items into two stacks?

[aierce]

If I have a stack of 20 antimatters, how do i split that into 2 stacks of 10 antimatters?

[Maarschalk]

For example i have one stack of 20 antimatters
How do i split that into 2 stacks of 10 antimatters?

The only way to do this is when docked at a Station and you have 2 Cargo bays and the first top Cargo bay is filled with something else and your second bottom Cargo bay has the 20 units of antimatter.

First sell whatever is in your first Cargo bay and then I believe when you right click on your second Cargo bay it will transfer 1 unit with each right click at a time to your first Cargo bay. So right click 10 times on your Second Cargo bay!.......