Inactive subscribers are people who have interacted with your account, but either
never joined a List.
or are no longer contained in a list.
Inactive subscribers are not the same as Opt-outs. You can view these numbers by going to Subscribers > View all > Filter > "Inactive".
Your Keyword is triggering an auto-response but not opting people into a List.
Your long code is not opting people who text it to a List. When someone texts your long code, their message will be sent to your Inbox, but they will not be part of a List.