Click and hold to have a chargeable bar appear on your screen. It'll quickly rise and lower. The closer the bar is to being full, the further you can throw the grenade. Let go of your mouse button when it's within a reasonable range of where your target lies. Be careful though - you can also be damaged by this grenade, which does 60 damage.
Data is not updated in real time. Most stats update within seconds or a few minutes.