In-App Purchases

Hello,

I have downloaded 2 applications for Habit Tracking & liked them both.

To have access to premium features, it needs in-app purchases.

Now, one app says in the description that:

In-App Purchases

• Lifetime Premium Membership$5.99
• Lifetime Premium Membership $3.99

The other one says:In-App Purchases

One-Time Premium Upgrade$3.99

What is the difference between these two?

Thanks!