It is recommended that you aim to eat your target calorie amount every day but it's unrealistic to think this is always possible.
If you over or under-eat throughout the week try to balance your weekly calorie total at the end of each week by checking your 'week-to-date' calorie figure on your 'weekly summary'.
Losing weight at a steady pace is preferential and more sustainable over time than quick weight loss.
Balancing your week-to-date figure to zero to achieve a successful weigh-in is the most sustainable over longer time periods.
You won't be able to sustain an overly restrictive diet for very long and you could be putting your health at risk.