How know if an index is used? - response (6) by mybudy

Yes , I am refering to access count of indexes, but if my secundary index is the tuple (nu_phone,cod_central) and the access count is 29 for the column nu_phone and 3 for the column cod_central then , how many time is accessed the index ? 29 or 3 ?

Example (dbc.indicesv) : 

.... indexname , columname , columnposition , accesscount .....  -->

myIndex1 , nu_phone, 1 , 29    --> row1

myIndex1 , cod_central,2,3      -> row2

myIndex2 , co_region,1,960  --> row3

myIndex2 , co_state,2, null -->     row4

myIndex2, co_store,3,247 -->     row5

The question : 

how many access have the index "myIndex1" ?   29 or 3 ?  

how many acces have the index "myIndex2? 960 or 247 or null ???

why the access to column co_state in the index "myIndex2" is null ?

I understand if you access to index (all columns)  then the number of accessed to columns of index should be the same , true ?
Thaks.