Hamas claims only 48 gunmen killed. The IDF explains why this low figure is laughable. YNet News writes:
Israel estimates that 500 Hamas gunmen were killed in the fighting, but is also taking into account that in some cases it was difficult to differentiate between gunmen and civilians, as some terrorists wore plain clothes when they were unarmed. According to the army, the gunmen were able to travel unarmed as numerous structures throughout the Strip served as weapons caches. Therefore, the IDF said, some of those were counted as civilian casualties were actually gunmen.
Minimizing its own casualties figures has great value for Hamas. By inflating the number of deaths defined as "civilian," the greater the moral and legal pressure can be placed on Israel.