OpenTTD

For ease of discussion I attached a screenshot showing a sample multi-level vehicle group.

First, I understand that in "Level 2" the grayed out entries are those that belong to the subgroups, this has no problem.

However, the number of vehicles shown on the left panel (i.e. the column at which the yellow arrow is pointing) may be confusing.
"Level 2" is displaying the figure of 1 - one vehicle which is in the group, but not in any of the subgroups, but some may be thinking it should be displaying 1+1+3+4+0 = 9

A similar problem is also seen in "2A", it may be debatable on whether it should be 1 or 1+3+4 = 8

To tackle this problem, there may be three solutions:
(1) Leave it as it is and add to the documentation that the numbers are meant for the vehicles that belong to that group at that level exclusively, but that is not very reasonable as many would expect a sum of the group and the subgroups from a mathematical perspective.

(2) Display the total number of vehicles in that group and subgroups
i.e. Level 1 would show 0+2+1+2 = 5; Level 2 showing 9; 2A showing 8 and so on.

(3) Display both figures in the form
(Number of vehicles in group only) / (Total number of vehicles in group and subgroups)
i.e. Level 1 would show 0/5; Level 2 showing 1/9; 2A showing 1/8 and so on.