Guild Wars 2

I have maxed Guardian Virtues for +30% boon duration, x2 Runes of Water for +15% boon duration, x2 Runes of Earth for +20% Protection, and x2 Runes of Water for +20% Regen. This should give +65% Protection and Regn.

For an example, the Protection granted by the 3rd hit in the #1 Guardian Hammer chain is originally 1 second.

After adding runes and traits, however, my tooltip says it’s duration is now is 1 1/2 (1.5) seconds when it should be 1 13/20 (1.65) seconds.

So I wondered:

a) is there a flaw in my reasoning

b) is the tooltip wrong and it is actually 1.65 seconds.

c) Or is the duration rounded to the nearest 0.5%, and thus the +15% provided by the 2x Runes of Water are useless?

Thrumdi.9216:

I have maxed Guardian Virtues for +30% boon duration, x2 Runes of Water for +15% boon duration, x2 Runes of Earth for +20% Protection, and x2 Runes of Water for +20% Regen. This should give +65% Protection and Regn.

For an example, the Protection granted by the 3rd hit in the #1 Guardian Hammer chain is originally 1 second.

After adding runes and traits, however, my tooltip says it’s duration is now is 1 1/2 (1.5) seconds when it should be 1 13/20 (1.65) seconds.

So I wondered:

a) is there a flaw in my reasoning

b) is the tooltip wrong and it is actually 1.65 seconds.

c) Or is the duration rounded to the nearest 0.5%, and thus the +15% provided by the 2x Runes of Water are useless?

Has anyone ever found an answer to how +Boon Duration rounds? I’ve searched the entirety of the forums and the entirety of the internet and no one seems to know.