What is the BLEU score used in Google Brain's "Attention Is All You Need" paper?
BLEU (Bi Lingual Evaluation Understudy) is an algorithm for evaluating the quality of text which has been machine-translated (MT) from one natural language to another. BLEU is typically measured on a 0 to 1 scale, with 1 as the hypothetical “perfect” translation. 

Google uses the same definition of BLEU but multiplies the typical score by 100.