Answer first
Followers are accounts that follow you; following are accounts you chose to follow.
The two lists overlap but are not mirror images, and the overlap is the mutual set.
Worked check
GroupSet ruleExample
MutualFollowers ∩ Following1209
Not following backFollowing − Followers376
You do not follow backFollowers − Following222
Read the relationship state correctly
The check compares two present-tense sets. “Outgoing only” says where the username appears now; it says nothing by itself about intent or history.
Choose the set that matches the question instead of treating follower count as the whole story.
Context before action
Comparing only the two totals hides which specific accounts create the difference.
Mutual status can change after the export, so verify accounts that matter.
Choose the next step
Review the relevant group and leave intentional one-way relationships alone.