added matter---how to define it

[cmabill]

I have a pending application, the examiner think I am adding matter but I think I am just clarifying the technical that I didn't specify clear and correctly? anyone has input on this.

my drawing has a board without M9 hole, and board with few M9 holes, both are showing clearly on the drawing, but I didn't mention the board without M9 hole in my description. now could I amend it and include " the board without M9 hole" in my claim?

personally I think this is mistake or negligence, but it seems the examiner didn't think so, because he think I didn't mention it in my description. pls help.