Hi I'm having a hard time deciding the actual resolution size for 320 dpi

In android developers page it says that the 320 dpi is like 2560 px that would be xhdpi

but they are too big I switch to using the buckets base it on a 10' instead 1280x800 and put a dpi of 320 but im not sure if this is correct

Does any one knows whats the good most standard size to use for design not coding for xhdpi and hdpi ?