Under the Free plan, you can make 50 images every 24 hours. However, this is a rolling window of time so it doesn't reset at a given window of time (e.g. midnight). As time elapses, you'll be able to make more.
In the meantime, you'll be rate limited when you go past 50 images. You can make more but you must wait.
If you want more than 50 images per day, you can buy a paid plan to increase your quota per day at https://playgroundai.com/pricing.