Difference between the SUBTOTAL(103) and COUNTA?

Hi all,

I have a problem. In some cells A1:AD1 are the texts, the rest are empty.

1. If I mark A2: Z2 and introduce a formula

=--(COUNTA(OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5)

completed Ctrl + Shift + Enter in these cells have values ​​0/1

2. If I mark A3: Z3 and introduce a formula

=--(SUBTOTAL(103;OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5)

completed Ctrl + Shift + Enter in these cells have the same value as in the case of using COUNTA in step 1.

3. If you have a formula for A4

=IF(SUMPRODUCT(--(SUBTOTAL(103;OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5))=1;"OK";"")

in the A4 I have the result of "OK" or "" depends on the content A1:AD1

4. If you have a formula for A5

=IF(SUMPRODUCT(--(COUNTA(OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5))=1;"OK";"")

I have it in A5 #N/A (Ecel 2007) or ""

My question:
1. Why formula

=IF(SUMPRODUCT(--(SUBTOTAL(103;OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5))=1;"OK";"")

It is correct (result = OK) and the formula

=IF(SUMPRODUCT(--(COUNTA(OFFSET($A$1;;COLUMN($A:$Z)-1;;5))=5))=1;"OK";"")

It is no longer correct (result = #N/A or "")?

After all, and in step 1 and step 2 are returned to the same horizontal arrays.

2. In this particular case, what feature SUBTOTAL decides that the SUBTOTAL formula is correct?

Sorry, I do not know English

Thank you.

Tomek