Q:

Counting the total number duplicate specific values in 2 columns

I am using Office 2007 and have this formula 
=SUMPRODUCT(SUBTOTAL(3,OFFSET(K5:K254,ROW(K5:K254)-ROW(K5),0,1)),--(K5:K254="24""")) + SUMPRODUCT(SUBTOTAL(3,OFFSET(O5:O254,ROW(O5:O254)-ROW(N5),0,1)),--(O5:O254="24"""))

and appropriate one for each of the 17", 19", 22" and 23" monitor special row boxes that I need to have an accurate count of.
My problem is that for some reason the above formula will only count from K:K the number of monitors but will not do the same on N:N
I tried 
=COUNTIF(K:K,"24""")+COUNTIF(N:N,"24""")-COUNTIFS(N:N,"24""",O:O,"Personal")

but it will get me the circular reference warning error even if at first I do get correct number of monitors, but after the error flashes the value is 0.
My goal is to have a formula that can count from 2 separate columns (K and N) the exact number of company monitors minus the personal ones when I apply a filter in F-S monitors.
My data has 254 names of users with other details and for the monitor evidence data is listed as below:
K column has Monitor1: 17", 19", 22", 23" and 24"
L column has HP, Lenovo, F-S, n/a
N column has Monitor2: 17", 19", 22", 23" and 24"
O column has HP, Lenovo, F-S, n/a, Personal

Your help is very appreciated. 

A:

This is the same formula adjusted to apply to N rather than K:  
=SUMPRODUCT(SUBTOTAL(3,OFFSET(N5:N254,ROW(N5:N254)-ROW(N5),0,1)),--(N5:N254="24""")) + SUMPRODUCT(SUBTOTAL(3,OFFSET(R5:R254,ROW(R5:R254)-ROW(Q5),0,1)),--(R5:R254="24"""))  

Simply adding the two together might be what you want. 

