They are seeking a judgement based on the legal concept of patent exhaustion.
https://www.wikipedia.org/wiki/Exhaustion_doctrine_under_U.S...
If Apple buys a cellular modem from Intel, for instance, and Intel has already paid Qualcomm to use their standards essential parents to manufacture those cell phone modems, then patent exhaustion holds that Qualcomm cannot force Intel's customers to pay to license those patents all over again.
Until a judge rules on this, you really can't say that Apple owes Qualcomm anywhere near that figure.
There is more information on the FOSS patent blog:
http://www.fosspatents.com/2018/10/patent-exhaustion-keeps-q...
Edit: I think this FOSS patent blog entry from last month does a better job of laying out the basic issues.
http://www.fosspatents.com/2018/09/apple-foxconn-et-al-want-...