on my (and my friends) mac laptop the cargo capacity is not calculated with connected cargo space blocks. it shows as over capacity and will not allow me to add blocks in build mode (by un building them) when using as personal cargo but will in astronaut mode and will let blocks be added manually.

this is the linked cargo spaces

this is the unused cargo spaces

this is what the inventory displays the cargo capacity as

i believe the issue might be OSX only but i haven't tested on Linux so i didn't put it in the dropdown list.