Actually Nicki has sold more as a leading artist, only in the RIAA has certifications for 37 million singles sold and that only in the United States. Approximately Nicki has more than 60 million singles sold as a leading artist.

If SB is 8x for the RIAA and has sold 15 worldwide, there are 7 million more. Starships is 6x for the RIAA and has sold 13 million worldwide.
At 37 million in the US by the RIAA, we added 14 million of Starships and SB, are 51 million singles sold plus all the other singles, I would say that it has sold more than 60 million as the main artist