People knew Morning Musume from ASAYAN which was a pretty popular TV show back in the late 90s, also their indies debut was marketed pretty well with them touring the country.
Meetan should manage 10,000 in a month but I very much doubt she'll achieve that this week or the next for that matter, 10,000 copies in a week can often land in you at around #10 in Oricon. I bought a copy of the single but from YesAsia which doesn't count towards Oricon >_>;