Can someone explain this to me?

I tried to do:

Obsidian Flesh (21 sec duration @ 16 earth; recharge 30 sec)
+
Glyph of elemental power (next 5 skill get +2 attribute)
=
Obsidian Flesh (22 sec duration @ 16 earth; recharge 30 sec)

And with:
Enchantments last 20% longer on the staff
+
Blessed Aura @ 0 attribute (Enchantments last 10% longer)

According to this:

Obsidian Flesh (22 sec) * 20% (staff) = 4,4 sec
Obsidian Flesh (22 sec) * 10% (B. Aura) = 2.2 sec

So:
Obsidian Flesh = 22 + 4,4 + 2,2 = 28.8 sec duration.

It would be 1.2 sec from constant Obsidian Flesh.

The problem is that I tested it and it lasted for ~26.5 sec not 28.8 sec.

can anybody clear this for me:
Is it a bug or is this just wrong?

Blessed aura:

While you maintain this enchantment, Monk enchantments you cast last 10...30% longer.

Your problem is that Obs Flesh isn't a monk skill ^^

Try [wiki]Serpent's Quickness[/wiki] for perma Flesh.

You might be right there, dang..
ok, thank you.

lmao :P common mistake... i guess

reading ftw.......
just kidding, i did the same thing awhile ago

Note that GW does not do fractions so an enchantment will never last 26.5 or 28.8 seconds, they'd be 26 or 28.