I found the problem.
Lineage a had 5 speciation events and 5 extinctions.
Speciation events are events that splits the lineage and produce two or more separate species.
Extinction events are events where the whole species die out in a short span of time. It is called "the great dying".
In the image,speciation is represented when one line breaks into two lines. Extinction is represented with the dagger symbol.
