That's overthecap.com estimation that Autry and Mingo will off-set. They usually get it pretty close to right but not close to 100%.
Even if we sign players below 6M average salary, like two more Autry type-deals, we wouldn't be eligible for compensation picks. The cut-off salary for players who count into comp. pick formula can't be known yet but as of now, it's less than 2 million. If we sign 2 players who have average salary of more than 2 million and will have them on the roster for next season, we wouldn't be eligible for comp. picks.
Which is why collecting comp. picks at this point of the rebuild (especially 4th and 5th) is a bad strategy. And it's not something CB seems to be planning since he's been after so many free agents.
edit. In some cases NFL might still award them if the difference in salaries is very big. Like Moncrief at around 10M vs. FA around 2M. But we would need to keep the average salary low and not sign many FAs, like last year.