The answers are in the article and well articulated. Basically it comes down to those that are not amongst the verified dead (under rubble, blown to smithereen

The answers are in the article and well articulated. Basically it comes down to those that are not amongst the verified dead (under rubble, blown to smithereens, etc), plus those that are seriously injured and will die as a result of those injuries, plus the longer term toll of the current actions that have been taken to date against those in Gaza that will result in their death via disease, starvation, etc. It does not take into account those that will result from the actions continuing. Given the effects and consequences of majority of the civil infrastructure has been deliberately and systematically destroyed the numbers are likely to be an undercount, rather than anything else.