Hello and welcome!
One thing which experience has taught me from the BSD (I’m 4 weeks in), is that keeping an eye on the total (good) carbohydrates can be helpful in losing weight.
There are a few apps you can look at, but one I use is My Fitness Pal where you can enter your foods and see how they are made up in terms of carbohydrates, fat, protein, sugar etc.
So you can look at how your 800 calories is made up, and that gets even more useful when you get the hang of things and start making up meals of your own, following the principles.
I have relatively little weight to lose, and therefore decided I would set my total daily carbs at 20g on My Fitness Pal, but a lot of people here work to 50g. You then top up your calories with fat and protein, to make up your total calories. Fat is important as it makes you fuller.
So have a look at a site like MFP, and see what you think. I use Ketostix and can see that my low carb intake is driving fat burning, which I’m really pleased about!
Good luck, you will soon get into the swing of it, and if you have problems, just post and one of the really helpful people here will pop up to help