Bitmap-Number
This property defines which image among the ones in the bitmap strip referenced by the Bitmap-Handle property is to be displayed in the page identified by the Tab-Index property.
When the values are enclosed between parentheses, the Tab-Index property is ignored, the 1st value refers to the 1st Tab, the 2nd value refers to the 2nd Tab and so on.
 
Example - Modify a tab-control to assign a bitmap number to each page
procedure division.
...
  modify screen-1-tc-1
         tab-to-add ( "Page-1" "Page-2")
         bitmap-number ( 3 2)
         .
...