This number comes from Hamas, so I would take it with a grain of salt. Hamas intentionally uses its civilians as shields for their military equipment. Here is a quote from Hamas's 1988 charter:
"The Day of Judgement will not come about until Moslems fight the Jews (killing the Jews), when the Jew will hide behind stones and trees. The stones and trees will say O Moslems, O Abdulla, there is a Jew behind me, come and kill him. Only the Gharkad tree, (evidently a certain kind of tree) would not do that because it is one of the trees of the Jews." [1]