我不明白你为什么这样说?用英语如何说?我不明白你为什么这样说?请您从头到尾仔细的核算一遍,我已经将最一项加在里面了.不信,您自己算算看

I don't understand why you say this?

i just don't know why you said like that? please cheak it from the beginning to the end for a time ,i have already add the the last item in it .if you don't believe ,you can count it yourself.

I don't understand why you said that.Please check it again,I had added the last item in it.If you doubt what I say,count it by yourself please.

I don't understand why you said so. Please double check carefully. I have already added the last item in. If you don't believe in me, you can calculate that yourself.