Like much of arnolds teutonic approach to life, his masturbation schedule was carefully conceived and adhered to. Often, he would cut a phone conversation or training session short to rush home so as not to miss a scheduled wank.
Some of the guys at Gold's figured that Arnold's masterbation timing was the key to his phenomenal growth, so they tried to keep track of his wanks, so they could copy his routine. But, of course Arnold was too smart for them, and always misled them with false clues.
So to answer your question, the number of times a week he turned japanese is a closely held secret which he will probably take to his grave.