One credit is one regular-sized picture generation. If you want to make it bigger or run more steps (in my experience, this is less useful than it would seem),

One credit is one regular-sized picture generation. If you want to make it bigger or run more steps (in my experience, this is less useful than it would seem), then it can run up to 3 or more credits per generation. That's still 3 cents a picture. Compared to Dall-E and even Midjourney, that's crazy cheap.