Tracker resizes but doesn't refresh shortened text until you open/close the tracker.
Looks like it's using "Questie Tracker: 1/25" as a cut off.
Easy to reproduce if you have 0 quest and picks up your first quest.

Can also be reproduced:

1. Untrack all quests by shift-clicking tracked quests in quest log
2. Questie options -> Tracker tab -> click Auto Track Quests off if it was on and then back on.