If COUNTIF Help

My apologies - please see below, and attached, for a better explanation of my issue:

1.  I have a spreadsheet with data in it starting in Cell A7 and finishing in Cell M1000.  However, for the purpose of my formula, I am only utilizing Columns A, G, and I:
   
   
   1.  Column A (unique 10 digit values always starting with an H in Cell A7; the length will always be different, but no longer than cell A1000).  Example values are H123456789, H987654321, H543219876, and H987612345.
   2. Column G (extract with unique and duplicate matching values always starting with an H in Cell G7) that has to be compared against column A, cells A7 – A1000.  Examples of the values are H123456789, H123456789, H123456789, H543219876, and H987612345.
       
   3. Column I, which contains the actual formula starting in cell I7 and runs through the end of extract (again, never over 1000 rows long).  An example of the formula from Cell I87 is:
      
      =IF(COUNTIF($G$7:$G$1000,G87)>1,IF(COUNTIF($G$7:G87,G87)=1,"1",""),IF(COUNTIF($G$7:$G$1000,G87)=1,IF(COUNTIF($G$7:G87,G87)=1,"1","")))
      
      
2. For every unique or duplicate instance in Column G (i.e. H123456789, H123456789, H123456789, H543219876, H987612345), that matches a unique value in Column A, I would like to assign a “1” to it in Column I.  If Column G contains blanks, zeros, or non-matching value against Column A, I would like to show a null value in Column I (with “”).
   
   
3. When applying this formula in Column I (I7 through I1000), it works correctly every time.  However, wherever my last matching value is in Column I, the very next cell in Column I shows a “1” as well, when it should, in fact, show a null value.  Ultimately, whatever the right answer is, it always comes up 1 more than the anticipated answer because of the extra (1 after the last match).
   
4. I suspect the extra “1” after the last match in Column I is because for every cell in the Column G range (G7 - G1000) there is an =LEFT(FXX,10) formula contained within, which truncates values originating in Column F and places them in Column G to start with.  When you look at Column G you don’t see the formula (range G7 through G1000), although I believe Excel does as a text value because of the =LEFT formula contained within.

Ultimately, no matter where my formula stops in Column I, I would like to eliminate the extra “1” in the following cell. An example would be if my last matching value is in Cell G87, I would like to get rid of the extra (erroneous) value of “1” in Cell I88.

Again, thank you.