"Extra fee" is basically YQ *) . For some reason (I assume tax regulations in different jurisdictions) they are keeping this fake tax on some routes/markets while they have abandoned it on others. This makes it even more difficult to know what a ticket will earn.
In the example adding this fee to the earnings doesn't change the outcome. Less earnings in the future.

*) And in the case of AY YQ is called YR: Carrier-imposed surcharge (YR)