When my WhatsApp is still open, in the box at the bottom when you double click the home button, my usage time keep on running. When phone is charged and usage and standby start at nul and whatsapp open, it will remain the same. Bad about this is, that when you calculate your usage, it seems ok as the running time is the a lot! Why is whatsapp reacting like this? It's the first app that I experience this behaviour.