Except... not really. Barbra was behind Britney on the counting chart by miles and her actual sales were so much lower UNTIL they included Barbra's sales from her tour ticket bundle. That gave her an enormous boost and shot her to #1. It's just clever marketing, nothing else.
Britney Jean, at Britney's worst musically, sold 700K worldwide which gives me higher hopes for Glory. Is she going to pass a million sales mark in the US? no, she won't, but with streaming included we might actually cross one million sales worldwide this time around and isn't that exciting?
The fact that Britney, twenty years into her career and without juicy ticket bundles, managed to outsell so many of the current and major acts like Meghan, Sia, Fifth Harmony, Selena, Demi is absolutely amazing. The industry isn't the same anymore, with a few exceptions for people like Adele, Taylor and Beyonce sales really aren't that high. Even Rihanna who is the worlds biggest pop star right now sold only like 55K more. This says a lot. Selling close to what Hillary Duff sells? on what fucking planet? Hillary sold 39K first week. Glory would've gone #1 on a quiet week and those numbers are extremely respectable.
And your argument about Janet and Unbreakable selling more... really? Unbreakable was Janet's first record in almost 9 years and she hasn't released anything since 2008. It also came with an announcement of a worldtour. Sure there was going to be more hype and anticipation. Britney was coming off a shit album and shit single (Pretty Girls) when going into Glory era yet it only sold 1K less... so honestly, this comparison is unnecessary.