I’m assuming that “Credits” is a number parameter in your user’s collection.
Add a Date parameter to the collection and call it “Reset date”. When the user signs up, set this automatically to “Date & Time > Current Time”.
Last, set the countdown finished action to update the logged in user. Set the amount of credits you’d like (in this case, you said 30) and set the reset date to the current time.
If a user has 30 credits on day 1 and uses 15 credits, on day 7, the credits reset to 30 if the user logs in. The countdown timer will only reset when the user visits the home screen after the 7 days.
So if the user uses 30 credits but doesn’t log in for 30 days, when the user logs in on the 30th day, it will reset the credits and set a new reset date.
It will not affect the logic since the countdown timer isn’t being reset while it’s hidden. It only gets reset when it’s displayed.