At the top of a second page, put the heading “Acts of kindness.” On this one, list all the positive things you’ve done for others. It might be the time when you helped a friend with their homework, when you did the ironing without being asked, or when you baked cookies after the family had had a tiring day. Whatever it is, no matter how small it might seem, write it down.

上面这段选2023年高考英语新全国卷1的阅读七选五。

请问为什么这里在序数词前用不定冠词，而不用定冠词呢？

请不要只是说理论，要分析一下这里的特殊用法在哪里，非常感谢！

附全文如下:

Personal Forgiveness

Taking responsibility for mistakes is a positive step, but don’t beat yourself up about them. To err (犯错) is human. It’s just as important to show yourself some forgiveness. You can use the following writing exercise to help you do this.

In a journal or on a piece of paper, put the heading “Personal strengths.” Now list all the characteristics you like about yourself. Are you caring? Creative? Generous? A good listener? Fun to be around? They don’t have to be world-changing, just aspects of your personality that you’re proud of.

At the top of a second page, put the heading “Acts of kindness.” On this one, list all the positive things you’ve done for others. It might be the time when you helped a friend with their homework, when you did the ironing without being asked, or when you baked cookies after the family had had a tiring day. Whatever it is, no matter how small it might seem, write it down.

You could ask a friend or family member to help add to your list. They might even like to have a go at doing the exercise. That way, you could exchange thoughts on what makes each of you special and the aspects of your personality that shine through. In fact, don’t wait until you’ve made a mistake to try this — it’s a great way to boost self-confidence at any time.

It’s something of a cliché (陈词滥调) that most people learn not from their successes but their mistakes. The thing is, it’s true. Whatever the mistake, remember it isn’t a fixed aspect of your personality. We’re all changing and learning all the time and mistakes are a positive way to develop and grow.