Statistically that means more adult were killed compared to the general demographic distribution of Gaza. Around 56% of people in Gaza are younger than 18.

Age structure (2018 estimate) from wiki:

• 0–14 years: 44.1%
• 15–24 years: 21.3%
• 25–54 years: 28.5%
• 55–64 years: 3.5%
• 65 years and over: 2.6%

https://en.wikipedia.org/wiki/Demographics_of_the_State_of_Palestine