You can utilize our "Likes Randomness" feature. This feature allows you to set a specified range of likes that you want to receive. Therefore, you can purchase the 100 likes / post plan and then set your desired range. Make sure to uncheck the box for "Always deliver 100 likes/post" to be able to move the slider.
You can set the likes you want to receive in your dashboard. Once in your dashboard, click "Targeting & speed settings".
You can see the "Likes Randomness" feature here.