Quarantine question

[Juice780]

I’m just starting my tank and am starting an observation quarantine tank to put each new fish in before it goes in my new tank. I purchased a tomini tang today at my local Lf’s. They have had it 2 weeks and it seems healthy with no issues. Can I count the 2 weeks they have had it towards my qt or should just plan like they just got the fish. How long do you leave a fish in qt before it goes into the main display?

 

[Malum Argenteum]

Can I count the 2 weeks they have had it towards my qt

Did they have it alone in a tank that didn't have fish of uncertain health in it previously? Was that tank not connected to the central filtration system? Did they not cross contaminate that fish/tank with non-disinfected nets or hands?