I really can't say, as I can't see inside your body.
I can say this, though, it doesn't send up red flags in my mind. You're starting out at a higher weight. It's your first month. You've drastically changed from your old eating habits.
20 pounds in 25 days is fast, yes, but you're still at the start of your journey, and most people do lose quickly at the start and then it ends up slowing down a bit as they go along.
If you go along for another month and you
still feel like you're losing too fast, then up your intake until you're comfortable at the rate at which you're losing.