Need a little help??

I just signed up a few days ago and trying to understand everything on the site. When I put my food in for the day I notice it grades you on everything you eat, I don't quite understand when I eat skinless frozen chicken breasts it gives me a D, I eat the portion size 100g and it's 100 calories. I thought that was good for me?? Does anybody know how the grading works?

Also, the pie chart at the end of the day I think is pretty cool that it shows you the grams and % of everything you ate but what does it all mean? How much sodium is a person suppose to consume in a day, how much fat to carbs to protein? Is there any information on this site for that or do I have to look elsewhere?? Any help on this would be greatly appreciated.

 Thanks.

I will let the more experienced CC'ers answer the second part of your questions, but about the chicken...are you selecting with skin and stuff with it?

If you are just doing chicken breast, click on poultry, then chicken and the first item is boneless, skinless chicken breast. When I put that in, I get a 'B'