Why do new gadgets need to charge its batteries at least 8 hours?

My collegue brought a new bluetooth set. The instructions ask her to charge the batteries at least 8 hours. Why? Does it really necessary?

How do you block, or at least assign to silence, “unknown” callers to Motorola Q?

On my cell phone, I want to ignore, or send directly to voice mail, callers from unknown numbers. Can anyone help? Thanks. I have a black Motorola Q phone.