Going over their wiki, it says that
QuoteWith estimated sales of over 50 million albums and singles worldwide, Little Mix is one of the best-selling girl groups.[2][3] According to the OCC the group has sold 18.9 million singles and 3.4 million albums in the UK.[
but the actual receipts show
Not to mention that overall, they've only sold 2.195M albums in the UK, which is ~1.2M less than what's stated;
There's no receipts of them selling 50M.