TL;DR
When reporting how many slots are used out of the number available in the item tooltip, take blocked slots into account, instead of reporting based solely on chest size.What ?
Item tooltips show chest availability, very handy especially when you are checking items from a distance: However, this can be misleading, if some (or all) of the container is blocked: Have the tool tip show that 4 out 4 slots are already used, or possibly 4 of 4 out of chest size 48.Apply to all containers that support blocking, specifically and especially including train cargo wagons.
Why ?
Less misleading: the current report suggests that 48-4=44 slots could still be filled, when in fact the chest is already "full."More accurate information, better decisions.