two different things.
maximum influence change is across all types of actions.
those actions have diminishing returns/a soft cap in itself. they are NOT linear.
in any system below 2 mio population you can't outlast max influence change with bounty hunting alone realistically, even if fully unopposed/no other traffic (check station reports).
you'll have to combine many different action/transaction types for that yourself or across your group.
you get 90% for ~4.5 mio of what you get for ~8 mio.
i have never looked into gains beyond ~10 mio, but if the curve goes on after that you'd need to redeem literally billions of bounties to get the max influence change in a small pop system.
the numbers and curves here still apply in game in my experience:
https://forums.frontier.co.uk/threa...ce-fc-update-bounty-buff.565678/#post-8961722