It is used to coerce an array of TRUE/FALSE to their 1/0 equivalents. For
instance J3:J300=J3 will return TRUE for each match, FALSE for each
non-match. Thus you get an array like {TRUE,TRUE,FALSE,TRUE,FALSE,...}.
The -- changes that to {1,1,0,1,0,...} which SUMPRODUCT can work with.

--
__________________________________
HTH

Bob

"Norbert" wrote in message
...
you are right, I've changed it to this:
=SUMPRODUCT(--(J3:J300=3),--(N3:N300Date_no+TIME(17,30,0)))
Also looks much better.

Can you please explain the "--" in the formula?


Bob Phillips wrote:
I wouldn't use 17.5/24 personally. Although it will likely make little
difference in this case, fractions are often not accurate in representing
time due to the FP processor in Excel.