官网上说

Some special LINE numbers used in the data files are:

21 = first new household member added to the roster in 1991
22 = second new household member added to the roster in 1991, and so on
31 = first new household member added to the roster in 1993
32 = second new household member added to the roster in 1993, and so on
41 = first new household member added to the roster in 1997
42 = second new household member added to the roster in 1997, and so on
61 = first new household member added to the roster in 2000
62 = second new household member added to the roster in 2000, and so on
77 = grandparent
88 = uncle/aunt
99 = other
-2 = guest

For LINE numbers 21, 22, 31, 32, 41, 42, 61, 62, etc., the first digit identifies the round in which the individual first appeared in the Household Member Roster (2=1991, 3=1993, 4 & 5=1997, 6=2000).

LINE numbers 77, 88, and 99 are used in the Childcare section of the Household Survey.

LINE number -2 is used in the Nutrition Survey.

而我在统计的时候

出现了1、2、3、4、5、6、7、8、9、21、22、31、32.。。之类的，，1、2、3、4、5、6、7、8、9是什么意思，是第一年也就是1991年就在调查内的人么？