就这样了 might be definitely the clumsy translation from "that it is". Did the Chinese suggest what context for the expression? You might ask him/her how to say 'that it is' in Mandarin, and that person simply translate it directly for you.
就这样了sounds very informal, even not serious, flippant to me. It has a negative connotation - I cannot make it better any more. I don't think it is appropriate for a serious spoken exam if a student says that to the teachers when he/she wants to finish his talk.
You can wait for other people to coment on "就这样了。”