densities for Android

Hi,

in this link : http://developer.android.com/about/dashboards/index.html

we see that hdpi density and normal size of screen represent 50%

but for this density and size, we have resolutions phones : 480x800, 480x854 and i have seen 600x1024 in table3 in this page : http://developer.android.com/guide/practices/screens_support.html

so, in my images/res-hpdi folder in my titanium project.

which size i will consider ? i dont understand well the concept..

thanks for you help.