Problem Description:

Excel auto filter behavior: http://www.contextures.com/xlautofilter01.html

after applying first filter, the second should only contain non-filtered data for selection

Reproducing Steps:

1. display attached file within Spreadsheet
2. apply "header 1" filter, select "1" only
3. apply "header 2" filter, it contains only non-filtered values only (i.e. a,b,d), select "a"
   
4. click "header 2" filter again

Expected:
filter should only contains non-filtered values for selection, i.e. a, b, d

Actual:
"header 2" filter contains all available values for selection.