Hi and welcome Melanie.
I am not a runner, but you will get lots of help, here.
A block is simply a balanced serving.
1 block of Protein is 7 grams of Protein.
Typically, 1 oz of most low-fat proteins (meats) = 7 grams of protein.
But it does vary, Fish is about 1.5 oz by weight for 7 grams of Protein.
You initially start by matching blocks of carbs and fat to your Protein requirements.
Since you are starting at 13 blocks of Protein,
then you also match 13 blocks of Carbs and fat.
A Carb block is 9 grams of Carbs.
Some examples: 1/2 apple. 1/2 orange, about 3/4 cup berries, 1 cup green beans, 10 cups lettuce, etc.
You see Carbs vary in volume by their density.
Fat blocks can appear a little tricky.
You want 3 grams of fat per block of Protein.
However, since most Protein has some fat in it, a fat block is 1/2 a serving or 1.5 grams of fat.
The remainder 1.5 grams of Fat are accounted for in the Low-fat Protein.
3 almonds is 1.5 grams fat.
Hope this helps get you started.