I started using my AI credits in early September, it is now October and my credits didn’t renew! I use a free account and it said it would renew in early October and it is October and my credits are at 0%! Google says this is a bug and other people had this issue so I think its a bug.
I checked my one and yes it also has not renewed. It will probably come sooner or later or maybe it is a bug. 
Hello,
Free accounts get AI credits over a rolling 30 days.
This means that credits you used on a given day become available again 30 days later.
Your early-September requests will free up over the next few days, on the same dates in October.
Hope that makes sense.
So if all the ai credits finished on October 25th then it will go back up to 100% on September the 25th not the start of the month (did i understand correctly?)
Close!
You’re right that if you used your last credits on September 25th, you’ll be back to 100% on October 25th.
But credits come back progressively: each request’s credits return 30 days after you made it. So the ones you used in early September are already coming back in early October.
We’ll look at improving the messaging about this.
ohh thats pretty smart- I actually never thought of that.