Condition Durations on Bosses

I was wondering, if you use Signet of Midnight on a boss with halved condition duration (like anyone in Tyria) and inflict blindness for 7.5 seconds, but then transfer your 15 seconds of blindness over with Plague Touch or something, will the blindness then last another 7.5 or so seconds, or will it last 15 like it did on you? (Sorry if that sounded confusing )

New condition of same type will replace the old one so your condition's current status will be transferred to the boss and the current duration will be halved.

All conditions inferred onto a boss, whether directly or via Plague Touch will have its duration halved at the point it is applied to the boss.

So, in your example, if you first apply blindness to the boss, it expires after 7.5 seconds. If you use Plague Touch on that boss right after it expires, the boss will be blinded for another 3.75 seconds (your remaining 7.5 seconds x 50%).