Anyone with a present Hamas connection is a valid target. Why do you say they're wrong in counting them as combatants?
Because the legitimate government of Gaza is Hamas, and the government employs teachers, nurses, administrators, civil servants, and so on.
Except the Hamas casualty numbers now reflect those "police."
As your own source revealed, they are included as policemen, as opposed to members of the armed brigades. Various members of Hamas may have reasons to include them or exclude them as martyrs rather than hapless victims, but there is no ambiguity around who they were, or how many there were.
The fact remains they were killed as part of a sneak attack in the middle of the night, simply for being members of the police force.