Your RDI is calculated to get you to a place where you are optimally losing weight, and you should be in that zone most of the time. If you don't make it every day, don't worry about it, but make sure to not go over.
You can safely shave off a few hundred extra calories, but where Fatsecret has set you is generally a good idea to stick with. Also, having the calories that you are allowed make losing weight a whole lot easier.
"Keep your friends close, your enemies closer, and the cookies at the other end of the table."
"Eating less, moving more, not eating stupid s**t = losing weight."
"Do. Or do not. There is no trying."
- Master Yoda.
I started my weight loss journey on October 4th, 2010 - and this is what I have accomplished so far: