For example, let's say I have a Strange Scattergun with no parts attached and no kills.
I kill 5 medics, then apply a 'Medics Killed' part to the Strange Scattergun.
Then, I kill 5 more medics.
What stat will be displayed? 5 medic kills, or 10 medic kills?
Or another way of phrasing it - will strange parts reflect statistics you accrued before applying the part? Or does it only start counting those statistics after it's been applied?