Hopefully, I can make this simple!

In H9:H400 and J9:J500 I have dates, manually inputted. In K9, I have this
formula: =IF(SUM(H9-J9=0),"-",SUM(H9-J9)), which formula carries down, of
course to K500, calculating the number of days difference between the two
dates. Column K is formatting "Accounting", so when the two manually input
dates are the same and there is no difference in days, then it enters a
simple dash. That all works fine. Now, the question: In I4 I want to put a
formula that counts all the ones that have no difference. I want it to start
with that if there's nothing to put nothing, otherwise count the ones that
have no difference. I tried this:
=IF(COUNT(K8:K500)=0,"",COUNT(K8:K500,"0")) but it doesn't work. I replaced
the "0" with "-", but still it yields nothing. I will have several down the
spreadsheet that will have no difference in dates. I want it to keep a
running total of them. How?