The percents of most recipes here start at 100% flour, which is the number you reference for the rest of the ingredients:
Example:
1000 grams of flour (100%)
600 grams of water (60%)
20 grams salt (2%)
2 grams IDY yeast (.2%)
Example 2:
2000 grams of flour (100%)
1200 grams of water (60%)
40 grams of salt (2%)
4 grams of IDY yeast (.2%)
As you see above, you can scale your recipe up or down using percentages.
Example 3:
I want 3 balls of dough at 400g each using the percentages above:
1200 grams total = 100% + 60% + 2% + .2% = 162.2%
That means the amount of flour is 1200g / 162.2 x 100 = 739.83g
From there you can put the rest of the recipe together:
Flour (100%) 739.83g
Water (60%) 443.9g
IDY (.2%) 1.48g
Salt (2%) 14.8g
John