Pseudo Sets - Behavior Push
Create and communicate clear ‘pseudo-sets’ to persuade people to complete a certain number of tasks (you've read 1 out of 4), encourage a specific number of donations (donate 6 packs, 1 for each family member), or buy a group of products (collect all 5 candles). People will stop at the reference point you set, but they are much more likely to reach it rather than abandoning earlier.
Works because of Unit Bias