All of them are not here means some of them are not here.这句的

三者以上的否定用none,所以此句的全部否定用none.用all .not 只是部分否定.
both 只能指两者.而 “两个都不” 才用neither.
楼主的句子：All of them are not here means some of them are not here.正是解释all.not是部分否定的意思,即：All of them are not here 就是指some of them are not here