I wouldn't be surprised if they're already close to the 50k mark and this will become their highest selling single by tomorrow. Even if they've only managed to sell equivalently as much as aitai or kimi wa jitensha over the last few days, added to that bumper first day this would be the case.
Apart from that UF have so far won the media battle like they've done with MM, the perception is C-ute is on the march and that they're easily one of the best Live performers in the business right now (which the members have managed by simply being awesome over the last couple of years).