Upvote:1
Unlike, say, US visas, Schengen visas do not only need to be valid on the day of entry but also define how long you are allowed to stay in the area.
So if your visa sticker says “8 days” under “duration of stay” then it means you can only stay 8 days in the Schengen area under this visa. Similarly, you must leave the Schengen area before the end of your visa's period of validity, so before or on the 27th of July (unless you obtain another visa or status in the meantime obviously).
The whole “90 days in any 180-day period” business is only relevant for people who don't need a visa (in which case the maximum stay is always 90 days) and for visas that explicitly say “90 days” or possibly “XXX” under “duration of stay” (which should in principle be the case for all multiple-entry visas with more than 6 months validity and not necessarily all that relevant for shorter visas but that's another issue).