When you cook with oil in a pan, not all of the initial 30ml will be absorbed by the food. Some of the oil will evaporate, and some will remain in the pan. The amount of oil absorbed by the food and the amount that evaporates can vary depending on factors such as cooking temperature, cooking time, the type of food being cooked, and the surface area of the pan.
Oil has a lower boiling point than water, so as the pan heats up, some of the oil will evaporate into the air. This process is more pronounced at higher temperatures and with thinner oils. Additionally, some oil may be left on the pan's surface or drip off the food during cooking.
As a result, the actual amount of oil that gets absorbed by the food is usually less than the original quantity you used. However, it can be challenging to determine precisely how much oil is absorbed versus how much evaporates or remains in the pan.
For calorie counting purposes, it's generally recommended to use the original quantity of oil you added to the pan in your calculations. This approach ensures that you account for the maximum possible caloric intake from the oil. If you are closely monitoring your calorie intake, it's better to slightly overestimate the oil's impact than to underestimate it.
Keep in mind that while oils do add calories to your dishes, they can also contribute essential fats and flavor. Moderation is key, and using healthier oils in reasonable amounts can be a part of a balanced diet.