When the number or amount of something stops changing, you can say that it has "evened off".

You can use this phrase when:

• a number or amount was getting bigger, but then it stops
• a number or amoun was getting smaller, but then it stops

As an example, think of the number of people who visit a beach each month. In the cold months, not many people visit. As the weather warms up, the number of visitors grows. Then, during the warmest months, the number of visitors "evens off". As it starts to get colder again, the number drops, and then evens off again in the coldest months.