Again, not necessarily. It MIGHT reduce earnings. Medium Help explains that an average percentage is calculated:

After all of the above engagement points and bonuses have been applied for a given story on a given day, we do one last adjustment to help correct for clickbait and other forms of attention grabbing that the story ultimately wasn’t able to deliver on. Stories with a lower than average read-through rate will be adjusted down in earnings, and stories with a higher than average read-through rate will be adjusted up in earnings. Read-through rate is calculated as: Total number of members who read your story for 30+ seconds / Total number of members who loaded your story

So really, a single action shouldn’t hurt, but if a lot of readers do that, it will.