your math is off because you can not multiply 16,66% 4 times and get a % that is lower then it's self. if you are basing your math with percents then you have to have a base number to work with Also he sold the titan chest 4 weeks in a row. Also you used only the warlock chest which there is only 2 of, so if Xur is going to sell a chest you have a 50% chance get the VFV again. The rng for Xur works like this First rng picks the types of gear that will be sold Second rng pick which items will be sold you can't base math of flawed concepts because then you will always get the wrong answer.