Endless Tincture of Fractional Power

Something I'm a tad confused about here. You put on a flask, say Flask of the Vast Horizon which lasts for one hour. But you use this trinket that copies the flask buff, at a fraction of the power and lasts 25 seconds. What happens to the Flask of the Vast Horizon buff? Does this thing increase that buff (the original power plus the fraction of the original power) for 25 seconds reverting back to the original power level for the remainder of the hour? Or, does it over write the Flask of the Vast Horizon buff for a weaker buff that only lasts 25 seconds?

Here's a shocker, the tool tip isn't very informative on this.