The website you linked to specifies a subtly different thing from what you’re asserting:
>”Forty-eight percent of the people who died from blast injuries among our colleagues' households were children and 40 percent were under 10 years old.”
That is quite different from saying that “ 40% of the bombing victims in Gaza are under 10 years old”.
The text does not say "of those children", the text says that 48% of the whole are children, and 40% are under 10 years. I agree it's a little ambiguous, but I read that as meaning that 40% of the total bombing victims were under 10 years.
>”Forty-eight percent of the people who died from blast injuries among our colleagues' households were children and 40 percent were under 10 years old.”
That is quite different from saying that “ 40% of the bombing victims in Gaza are under 10 years old”.