I don't know if anyone else has found this bug yet
Either Ashe's new passive tooltip is bugged or the one on the NPC's is
Either Ashe's new passive tooltip is bugged or the one on the NPC's is
Ashe shouldn't slow by 49% at level 14 (it becomes 35 at max level, I think). It's probably the passive tooltip that's wrong.
it looks like the tooltip is incorrectly adding the bonus from your Q, even though you haven't used it.
At level 15 (the level in the images), Ashe's passive should slow for 29%, which is how much it shows the Blue Sentinel as being slowed for. In this case, the passive is working as intended, and therefore the tooltip is bugged.
What is likely going on is that the passive may be accounting for the slow being the base with the extra slow from a rank 1 Ranger's Focus, which is weird because Ranger's Focus is at rank 5.
You might want to do some more testing with each of the different slow % thresholds, between Frost Shot's slow and with different ranks of her Q, to help see exactly what the tooltip problem is.