Oh you haters need to stfu
Brit kicked some asses having "3", an unpromoted single, going straight to #1 having a 250K first week slaes. The Singles Collection sales were bound to be low given the fact that she already has one out with pretty much the same songs, given the fact that this one only contains one new song. Most people who like Brit and "3" would likely buy the song from iTunes instead of buying an album with songs they already have.
I am still expecting more than 30K first week, and I am sure that the Box Set released in 11 days from now is going to sell much better. That's what most fans care for.