Correct the sentence I'm trying to say: "It's not true. You are sitting the fourth from the right side"

那不是真的。 你坐在第四个右边。

Is it correct?
As @user6065 suggested in the comment:

你坐在第四个右边 is weird in its word order.

By your context， I think you should say 你坐在右起第四个（座位） or 你的座位是从右数第四个.