no sure what is confusing.... ill go over it to help if i can...
Ranger's Focus
Applying Frost Shot grants Focus for 4 seconds, stacking up to 5 times. Activating Ranger's Focus consumes all Focus stacks, granting 20 / 25 / 30 / 35 / 40% Attack Speed and boosting Frost Shot's slow by an additional 20% for 4 seconds.
If 5 stacks are consumed, Ashe's basic attacks are replaced by a flurry of arrows resulting in 1.15 / 1.20 / 1.25 / 1.30 / 1.35 of her Total Attack Damage per attack for the duration.
if u hit Q before 5 stacks then you burn all ur stacks (use up the stacks) granting bonus attack speed per level, and boosting the passive slow for 4 secs.....
do u have further questions i can help with?