background里的一项，我怎么看不懂

ballpark

In order of importance to you, list honors, awards and/or areas in which you have distiguished yourself.  Indicate the date and basis for ezch selection,什么叫basis for each selection?困惑，请教大侠解答，万分感谢

diudiu

For example:
Dean's list, 1 out of 30

ballpark

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