有的,语法错误加上语义啰嗦可以改为i didn't understand what you said just now是哪些错误呢know后边的是从句，从句之后怎么能再加上is what mean呢？那这句话岂不是有两个谓语了吗，一个是前边的know一个是后边的is明显错误啊