I dont think that the chart is accurate because it doesnt ask how many times you rep the weight and everyone is differnt ex. I rep 205 10 times for 3 sets and my max is 335 and the chart gave me a way differnt number so.
Why don't you just max out? That's the most accurate way to find your max. That rep/ratio crap isn't accurate at all. Some guys can have a crazy high max, but not enough muscular stamina to put up less weight that many times.