It's an average. So although Spain have nine teams in Europe this year, one of them didn't make it out of the qualifiers, dragging the whole lot down.
Not sure what happens if a country only has one team in europe and they end up winning the conference league, maybe that country will end up...
It's not only an extra champions league spot but an extra European spot. A non top 6 league cup winner is a real possibility, leaving just the top 6 having European spots compared to a possibility of 8 or 9 at the start of the year