Hi angelalangbehn,
The numbers may be confusing but they are there as a guide and it may be easier to see it as an approximation rather than precise target each time.
You are right with planning your meals around the fat content first. Each gram of fat is 9 calories. Second you want your meals to stay under 500 calories.
The breakfast example: 300 calories. 30% fat calories is 90. if your meal contains 9 grams of fat (9 X 9) this equals 81 calories from fat which is close enough to 30%.
Hope this clarifies.
Sophia De Monte RPh