activity planning: how to interpret numbers

[pg788]

Hello
In the activity planning interface, some teachers have 0(+9) or 0(-1) mentioned. I understand that a 0 means that all target hours have been allotted. But what does the number in bracket mean? Not all teachers have this. Screenshot is attached.

[Volker Dirr]

the number in brackets is counted a bit different.
activities with one student sets are counted as always (each value 1 per duration).
but activities without students is not counted.
while activities with 2 students set are counted twice.

[pg788]

Oh, I see. Thanks a lot!