Personally I think these sales (while not bad) should be a wake up call to Team Britney. You can't just keeping doing little (or waiting until the week of) promotion. Yes her fanbase is loyal and demanding, but they also want to see her out working for it.
On the other hand, this could also be good news. Her albums need to have longevity and by not debuting huge, it gives them the opportunity to do more. Either way I'm fine. The album is great and Brit is having fun. That's all that really matters.
*if there are mistakes ignore it I'm on my iPhone*