Lost 1.8 lbs in a day?

You didn't lose 1.8lbs in a day.

day to day fluctions are just a fact of life.

Don't weigh yourself after 1 day. The difference between my weight when I wake up & when I return from work is usually around 4 lbs (I sweat it all). Go for weekly weigh ins then you'll see how much you lost.

Now when you first start you'll drop fast, thats just water weight, but after 2-3 weeks you're rate of loss will be steady.

Oh andAssuming you're 25 years old (Since you didn't state your age) your TDEE is around 2.5k calories if you exercise 5 days a week. You're net intake at best is 1700-350 = 1450 calories but you don't get that much every day.

Slightly increase cals if you want to lose 2 lbs a week, increase by 600 if you want 1 lb a week (Smaller loss is better in my opinion but thats up to you)

I sometimes lose that much in a day. Most of it is usually back the next day. Your weight will fluctuate up and down during your weight loss journey. If you consistently lose that much on a daily basis over a period of weeks, then it's too much, so you'll need to increase your calories to where you lose 1-2 pounds a week.