Saunalahti quick question

[menene]

I am a prepaid Saunalahti user and saw an interesting offer here: http://saunalahti.fi/prepaid/mobiililaa ... aketit.php (moderator, feel free to remove the link if feels like spam).

So I read:

Maksimi nimellisnopeus 384 kbit/s
Kuukausipaketti 1 - 6,80 €

Does this mean it lasts one month, like from 19th August to 19th September, or it lasts just from 19th August to 31th August ("one month")?