Whenever you put one or more time counters on a permanent you control, create a 1/1 white Soldier creature token.
Whenever Kate Stewart attacks, you may pay {8}. If you do, attacking creatures get +X/+X until end of turn, where X is the number of time counters among permanents you control.
Kate Stewart's first ability triggers only when you put time counters on permanents. It does not trigger when you put time counters on cards in exile.
Similarly, its last ability counts only time counters on permanents, not on cards you own in exile.